Twitter is poised to close a $50 million funding round that values the microblogging startup at a staggering $1 billion, according to TechCrunch and AllThingsD. Since closing its last venture round in February, then, the startup's value has grown fourfold.

Grown, that is, in the eyes of Silicon Valley's venture capitalists, slaves to the technology fashions for which Twitter is the leading model: real-time, micro, iPhone friendly and acquisition bait for Google. Twitter might say it's in this for the long haul — someone is spreading word the company has $30 million, or most of its last funding round, sitting in a bank account — but the company has proven far more adept at finessing moneyed suitors than in groping for reliable revenue streams.

Twitter's trend hopping founders, whose project management company begat their blogging company which led to their podcasting company which begat Twitter, seem more likely to seize on the easy exit of the former rather than the long grind of the latter.

Especially when, as these charts of their past investment rounds show, they're so very good at jacking up their price:

(Top pic: Twitter co-founders Biz Stone, left, and Evan Williams. By Joi Ito.)