On March 30, a core group of Yahoo’s Buzz Marketing team, which focuses on all kinds of nontraditional marketing efforts, is leaving the company to set up a new firm.

The name of the group of former Yahoo (YHOO) staffers–including Brian Mullin, Sean Florio, Mike Weaver, Kelly Delaney and Jason Anello–is Manifold.

“After a great run at Yahoo!, we’re looking forward to new challenges in the world of nontraditional marketing encompassing social, word of mouth, experiential and interactive,” wrote Mullin to me after I inquired. “Exciting times.”

Maybe for Manifold, but what does the departure actually mean for Yahoo?

Does it represent a worrisome and seemingly unending hemorrhage of talent? Or is it simply an example of ever-shifting and very normal staff movements within a company? Or what?

Probably all three, although when big-name employees go into turnaround situations–as has happened a lot of late at Yahoo and MySpace–stories mount that paint a direr picture than is perhaps fair.

“I actually think that is totally normal in any transformative phase, the cynics may decide in any one situation to make more of it, but when you reinvent, people leave, new ones join and current employees with history and new-found faith make a nice mixture,” wrote Jason Hirschhorn, co-president of MySpace, to me about the lagging social networking site that is owned by News Corp. (NWS). “Change is a catalyst for all of it.”

Which is not to say that some departures do not represent potential trouble. Yahoo losing its top advertising sales exec, Joanne Bradford, was very bad news for the company. She’s headed for fast-growing social media start-up, Demand Media.

And the ugly circumstances of the firing of MySpace CEO Owen Van Natta created great uncertainty at the worst possible time.

And with those departures comes greater scrutiny, especially internally, about the efficacy of comeback plans, as well as a nagging worry that there are much greener Silicon Valley pastures to be found elsewhere.

That said, in the fourth quarter, Yahoo actually brought on 700 employees, including about 250 from two acquisitions.

Some of the more prominent of those hires, according to a Yahoo spokeswoman, include:

• Sashi Seth joined as SVP, Search Products to lead the search business. Shashi brings with him a wealth of experience from Google, eBay, Cooliris, and AOL.

• Raymond Stern, joined as SVP BD & Partnerships, North America. Raymond joined from Intuit where he was SVP/Strategy & Corporate Development and spent more than ten years 10 years as a partner at The Boston Consulting Group.

• Bobby Figueroa, VP, Consumer Advertising Experience. Bobby joined from Google.

• Gil Yehuda, director, Open Source Product Management. Gil was most recently an analyst at Forrester Research and also worked at Fidelity Investments and Xerox.

• Chris Lehmann joined Yahoo! News as News Blog Deputy Editor. Lehmann is a former senior editor of Congressional Quarterly, political columnist for the New York Observer and features editor for New York magazine.

• Eric Adelson joined Yahoo! Sports/Special Projects Editor. Eric wrote for ESPN The Magazine from its inception in 1998 until the fall of 2008. He has also written for Newsweek, Details, and Boston Magazine.

• Manish Sinha joined as the Customer Advocacy team as VP, Global Customer Care. Manish spent more than 15-years at Microsoft.

• Mollie Spilman joined the CMO organization as SVP of B2B Marketing. Mollie has held key leadership positions at several companies including People Magazine, BH&G, Discovery Networks, Phase2Media, and TidalTV. She was also at Advertising.com for over five years, both pre and post AOL acquisition, and ran both the sales and marketing organizations.

• Deb Meyer joined the customer advocacy group as vice president of agency revenue and development. She joined Yahoo! with more than twenty years of industry experience, having most recently worked for AOL as head of US sales for Bebo. Prior to Bebo, she spent nearly a decade with Nielsen Online and more than ten years in the agency world, working for McCann-Erickson and Grey Advertising.

And while MySpace has seen an ongoing exodus too, there have been numerous recent entrants, according to its spokeswoman:

-New VP of Data Platform, Arvind Puri (was CTO of Buzznet/Buzzmedia, before that worked at the LA Times, Yahoo and Overture)

-New Senior Manager of Online Marketing from BillShrink, Tony Adam

-New Director of Tech & Product PR, Vincent Chang, ran his own consulting co w/Tariq Krim’s Jolicloud as a client, based in SF

Hellos to all, of course, which at some point have to be louder than the goodbyes.

In that vein, please enjoy this video of the Beatles classic:

On Wednesday, an always worthwhile Internet-focused conference, the annual Web 2.0 Summit, kicks off in San Francisco.

The lineup for the three-day event is particularly good this year and it is also a perfect time to take the temperature of the Internet’s movers and shakers, given all the hubbub of late with the weak economy. (BoomTown will thus be there with the trusty–and shaky–Flip video, chronicling it all for future generations.)

Speakers will include bicycle champ Lance Armstrong, Yahoo (YHOO) CEO Jerry Yang, former VP Al Gore, Google.org head Larry Brilliant, Paul Otellini of Intel (INTC) and Facebook’s Mark Zuckerberg, among others, chattering away on a wide range of topics. (You can see the full schedule here.)

There’s also, of course, a passel of parties, including one on Thursday night thrown by MySpace Music. And it will–shades of Web 1.0!–feature an exclusive performance by Lionel Richie (and also DJ AM).

I am, I shall admit it and without irony, a closet fan of Richie. And why not, with so much infectious fluff to choose: “Hello,” “Say You, Say Me,” “Three Times a Lady.”

Most importantly, I will be curious to see if there will be “Dancing on the Ceiling” among the beaten-down start-up crowd. (See that music video below and ponder exactly why you know you know each and every word to that funkadelic song.)

Hosted by Tim O’Reilly and John Battelle, the Web 2.0 Summit is called “Web Mets World” this year. By that, BoomTown is inferring that its organizers think it is time for the Internet to grow up. But why don’t we let them speak:

The commercial web is now a teenager—it’s been fifteen short years since Marc Andreessen released the Mosaic browser. To put this in perspective, television as a commercial medium reached its fifteenth birthday in 1956—the year Elvis Presley made his first appearance on national TV…as we pondered the theme for this year, one clear signal has emerged: our conversation is no longer just about the Web. Now is the time to ask how the Web—its technologies, its values, and its culture—might be tapped to address the world’s most pressing limits. Or put another way—and in the true spirit of the Internet entrepreneur—its most pressing opportunities.”

And, of course, here’s Lionel: