Since BoomTown constantly called the $15 billion valuation of Facebook “insane” when Microsoft (MSFT) forked over $240 million in 2007 and gave Slide’s Max Levchin a very hard time when his widget company got a $550 million valuation a year ago, it’s only fair that I say something equally appropriate about Twitter.

The hot microblogging service just got its very own $250 million valuation, all without a dime of revenue in sight. (I know, Bijan, it’s coming, it’s coming!)

After all, Facebook and Slide got their funding in boom times and here we are hurtling toward a possible Depression: The Sequel, even as Twitter hauls in $35 million more in investments.

But I am torn.

Should it be “WTF?” given that the current economic meltdown really seems to have little impact on Silicon Valley venture capitalists?

I guess they have to put their money somewhere and that’s probably the best choice out there, due to Twitter’s strong growth and, perhaps more importantly, overhyped media mindshare.

Or maybe: “Don’t Stop Believin’!!? I mean, you almost have to admire the appalling suspension of disbelief for Benchmark Capital and IVP to hand over such a sum.

In fact, they are probably right now down at at Il Fornaio in Palo Alto, telling everyone who will listen that Google (GOOG) was founded in the last tech downturn.

Actually, I think the only thing to say is to reference the search giant: “Let’s hope Google has another YouTube moment and decides it must own the start-up pioneering real-time search and status updates no matter the price.”

That’s kind of long, so I will distill it to this Calgon-inspired thought: “Larry and Sergey, take me away!”

Because while I appreciate that Twitter co-founder Biz–I can’t help it, but I laugh every time time I write his name in relation to a company that makes bupkis–Stone underscored that the company was ready to make some money using the new funding, an acquisition by a big, nervous Internet giant is the only way this is going to end well.

In his post, ironically titled “Opportunity Knocks,” Stone noted, “We are now positioned extremely well to support the accelerating growth of our service, further enable the robust ecosystem sprouting up around Twitter, and yes, to begin building revenue-generating products.”

That would be nice, because right now, there’s no Biz like no biz.

And not to sound like a skunk at this Silicon Valley garden party, but Twitter might want to start doing that sooner than later.

I know, I know, I am such a bummer with all this talk of things not just growing to the sky in a world without end.

But as Facebook–valuation now officially $3.7 billion, although probably more if it were to be sold–has found out, the delta between dreamy funding and revenue reality can be quite huge.

And, by that, I am not saying it can’t be done, I am simply saying: Do it.

Until then, here is a lovely Calgon commercial and also a video of that amazing last scene in the finale of “The Sopranos” with the Journey song playing until it is abruptly cut off (I say Tony was shot in the head by the guy in the bathroom, but please weigh in):

If that proves true–if the economy doesn’t hit bottom until the second quarter of 2009–this recession will have been the longest since the Great Depression. What a horrific thought….