> You don't need a vulnerability to spread spam on Facebook, so that's out. Page likes and video views can be done with botnets. Spreading malware doesn't make sense - it would be far superior to buy a vulnerability allowing direct desktop access, not one that will be patched quickly.

But using compromised accounts that belong to real people with a believable history is more effective for spamming. Of course you'll need botnets, but if the accounts look fake, rarely anyone will follow what you're saying. This is less of a big deal for page likes and views, but it can still be helpful as it will make your page's likes look more legitimate.

Using the accounts and pages of influential people (100k likes or so) to spread malware and advertise is a whole different beast than using some account without a profile pic to do the same.

Regarding personal information, yes I agree, it's definitely more limited in usefulness and not something worth $10k.

But for the rest I've mentioned, I'd argue that a large malware spreading service (yes, these exist) would find an exploit of such nature quite valuable.