Suppose my competitor has X number of backlinks and I want my site example.com to catch up with him. One way to get X number of backlinks would be to get X number of people on facebook to write somewhere on their profile / wall etc something like 'I bought a widget from example.com - those guys are awesome and I really recommend them'.
I think that google likes domain diversity so lots of backlinks from the same domain is not good. But on the other hand these backlinks are from different people ie many different people recommending example.com is surely different to and better than just one person recommending example.com, so it seems wrong to say that having 100 recommendations is no better than having 10 recommendations.
So any ideas please how google would evaluate this?