An elevator pitch is a short summary used to quickly and simply defineWhat was the elevator pitch of Facebook when it started?
a product, service, or organization and its value proposition.
Is there any good accurate description for Facebook?
Is there a current one for Facebook?
Getting Started Marketing Ideas Business Model
A short summary of what they do can be found everywhere written in different words.
If you are asking it to benchmark your pitch then most likely this will be a very difficult question to answer. Probably their "pitches" have been changed/adapted many times and often depends on the context (for example we don't use the same terminology for investors than for prospective customers or talking to relatives).
Personally I think the best source are interviews or chats with founders or top executives, where they explain the business to the readers/audience. Try to find interviews from the early days so you can compare how much they changed the way of pitching their business.
There are a couple of good youtube videos on elevator pitches out there.
I put some here:
http://www.youtube.com/watch?v=Tq0tan49rmc http://www.youtube.com/watch?v=i6O98o2FRHw
"is s/he available? find out now." Would be the likely facebook pitch.
Here's an expansion of that pitch + traction + potential + business model.
For more recent sites, view this video series on elevator pitches