"Me too" startups

I went over some of the sites in go2web2 and Techcrunch, and it's amazing how many copycats are out there. Just to name a few (in my view):

• Justin.TV - "Is a website entirely devoted to chronicling the life of one of the company’s founders, Justin Kan, around day and night via web cam" (JenniCam version 4.0?)
• Twitter and Dodgeball - Users establish a friends list to whom messages are broadcast - IM software with cell phones and SMS support. (but still same concept of the original ICQ)
• Flixster - "The Flixster movie community includes movie ratings and showtimes, movie reviews, movie layouts, movie pics & posters, movie news, video clips, movie fan clubs, actor profiles and fan clubs, celebrity news, celebrity photos, celebrity layouts, and the never ending movie quiz." - As far as I know IMDB has all of that, but Flixster is still a huge success - why?
• Joost - "A new way of watching TV on the Internet, which uses new and established technologies to provide the best of both the Internet and TV worlds." From the makers of Skype. This is actually somewhat new, but is based on the success of YouTube (and personally after watching shows from the net, when I want them and with no ads, I don't like the idea of taking the pre-net ideas of channels and ads into the web 2.0 world).

And there are many more Digg/Myspace/Blogger clones out there.

Don't get me wrong - if someone thinks he can take YouTube's concept and do it better, I'm all for it, but it seems strange to see VCs invest in those startups.

Is this the evidence we are in the height of a new dot com bubble?
Does that mean it's about to explode?