What I was referring to is the fact that they likely never delete your info, they just set disabled=1, recoverable=0. I have heard anecdotal accounts[1] and read the writing on the wall[2], along with a hunch, that they would rather not delete data unless compelled to. Disk space is probably the cheapest its ever been, and there's a lot that you could learn from one's profile data, and they undoubtedly data-mine (and probably sell) it regardless of your disabled status. A 3rd party might be
more interested in your data, say maybe if they determined that their demographic shows a strong inverse correlation with FB activity. Or maybe the 3rd party feels that they've already saturated the FB market, and is looking for leads in new markets. Facebook themselves would stand to gain from crunching numbers to try and determine
why people leave, since that is lost revenues for them.
Although, I hear that the EU (or maybe just the UK?) has strict provisions around keeping data, and so those users who choose to delete their account really do have their data wiped. But not the rest of us.
1. https://news.ycombinator.com/item?id=3145987
2. http://blogs.wsj.com/digits/2013/08/29/facebook-reminds-user...