During the heydays of web2.0, before the current economic slowdown, many social networks got funded and it is inevitable that there will be tremendous amount of consolidation in this space. Piczo, a social network for teens, and Stardoll, a website for girls are merging. I think this merger makes a lot of sense as the demographics are adjacent and therefore are synergistic.
Talking about social media consoldiation, diigo buys furl, a social bookmarking site.
Expect to see much more of this in the coming months.