Why would being "the new cool kid" affect job satisfaction ratings by employees? Unless you're suggesting they are more satisfied due to the coolness of the idea of working there.
There're a whole bunch of benefits that you get from working at the "cool new kid":
1.) Everything you do automatically has an audience. People care about the software you write and use it in their daily lives.
2.) You get social cachet from working there. Say "I work for Google", and a bunch of people will say, "Oh, that must be nice. I wish I was smart enough to get in there." Outside of a few nerds who are too cool for FaceBook, saying "I work for FaceBook" gets the same reaction.
3.) Being in a younger, game-changing company gives you the chance to work on cooler, game-changing technologies. Many tech workers are attracted by hard problems; young, fast-growing companies tend to have lots of hard problems.
4.) When companies are younger, they've accumulated less legacy code and fewer bureaucratic procedures. If you ask a bunch of Googlers what they hate most about working for Google, I bet a large portion will say "legacy code". This is a maintenance tax that isn't fun at all, yet has to be dealt with whenever you build something on top of it. Being younger and smaller, FaceBook has less of this.
#2 is a fair point, but I think you have it reversed on #1 and #3. You are a cool company _because_ you're young, game changing and have an audience, not the other way around.
#4 is a property of most young companies regardless of their popularity.
Don't forget about the 'halo effect'. If a company is performing well, it tends to lead to better results in employee surveys, for no other reason than that.
I know this doesn't exactly explain why facebook does better in the surveys than google, but I think part of the reason facebookers feel more satisfied, is because they know they get paid more than googlers.
1.) Everything you do automatically has an audience. People care about the software you write and use it in their daily lives.
2.) You get social cachet from working there. Say "I work for Google", and a bunch of people will say, "Oh, that must be nice. I wish I was smart enough to get in there." Outside of a few nerds who are too cool for FaceBook, saying "I work for FaceBook" gets the same reaction.
3.) Being in a younger, game-changing company gives you the chance to work on cooler, game-changing technologies. Many tech workers are attracted by hard problems; young, fast-growing companies tend to have lots of hard problems.
4.) When companies are younger, they've accumulated less legacy code and fewer bureaucratic procedures. If you ask a bunch of Googlers what they hate most about working for Google, I bet a large portion will say "legacy code". This is a maintenance tax that isn't fun at all, yet has to be dealt with whenever you build something on top of it. Being younger and smaller, FaceBook has less of this.