Google is getting a bunch of people who get social games (and social software in general) -- something they've historically been pretty bad at. Of course, they are buying the (distant) 2nd horse behind Zynga, aren't they?
I think Playdom is probably a lot larger than Slide... oh hrm and Playdom was just acquired by Disney for $763M. Slide is definitely small fries in comparison to Playdom or Zynga.