that comparison is founded! The google business model is extremely solid if you compare it to facebook, not only they are the leader in a vital internet need (search) a well deserved lead if you ask me but they also have "diversification" (Youtube, Chrome, Google earth, GMAIL..) google is everywhere.
Facebook on the other hand is just like the best restaurant or bowling center in town, people will give up "socializing" in facebook the minute a better "restaurant" or "entertainment" center show up in town, facebook killed myspace, and will face the same doom when the next coolest thing shows up.
and wtf, 70 billions for a company making a net benefit of 250 millions a year ? i know it's more complicated than that, but i can't help thinking that i'll need to live 280 more years to make my investment back.