People do click on FB mobile ads by accident. The screen is small, it is so easy to mistakenly click on the rather big ads. That explains the mobile CTR is much higher than that on the desktop ads, but much fewer fans converted on mobile devices than on the desktop.
For 1 billion users, if everyone accidentally clicks once, there is only one-time frustration for the user, but huge CTR and ads revenue for FB. That is why GRPN's stock was over $20 just several months ago because those small businesses need to be frustrated once to quit to try GRPN.
I dont get were everyone is sorried about FB users clicking on the ads. Of course they are. I see many cross my page were friends recommend them. I click on them, I've purchased items from the sites. It's safer than clicking on an ad from the basic internet. Plus they tune it to items you have looked at in the past. I think its a great feature. I enjoy it, so do my friends