Facebook profile photo -> google image search -> address or other accounts to attack

I am intrigued about situations in which you would have someone's Snapchat username, but so little of an idea of their name/network that you couldn't find them on Facebook with graph search.

A few months ago, I was trying to figure out what this Snapchat was all about, so I signed up with a fairly common username.

Sure enough, in a few days, I received several topless pictures from a random account. The girl typed in a name which she thought belonged to her friend, but instead entered my new profile name.

I thought this was hilarious, my girlfriend however, didn't. Just one random situation.

The contacts app on the iPhone does something like that last jump, where having a phone number + first name is enough for it to sometimes find the full FB profile and update the pic associated with the contact on the phone. I assume/hope it only works when they have their phone number public on their profile, though.

I guess for that to work you need to sync your Facebook Account and will only update/find full FB profile if they are in your friend list.

It doesn't do a common FB database wide search just from your contacts/FB friends.

Well, no. I have some fb profile (with photo) in my phone contacts of people that it's not in my friend list, but (probably) it's in my "friends of friends" list. So probably the latter is enough.