Web 2.0: quite established term, since Tim O'Reilly published his scene-setting & eye-opening article on that topic. Its mostly about user-experience, social networking and the like. Go read it, just in case you're not familiar with web 2.0.
Later came Identity 2.0 - a fantastic presentation. Even later cam OpenSource 2.0 (brief report in German)...
Then some sh** hit some fan: An undisclosed company came up with Security 2.0.(via Stefan). Which actually made me think of some further developments in this "too-dot-oh" direction: Is the term "nonsense 2.0" copyrightable? Or is this stuff just too-dot-oh-much for me?
By the way: I'm forty-too-dot-oh years old, and my cars' licence plate carries the number six-four-too-dot-oh. Gosh, somebody hopefully will find out that I'm modern-too-dot-oh.