This is basically how FBI Director Comey's secret Instagram account (and thus Twitter account) was unmasked. But it was even worse - you are suggested to 3rd party people who just follow the people who know you: https://gizmodo.com/this-is-almost-certainly-james-comey-s-t...

Yep, something similar I discovered recently that if you sign up to Instagram with somebody's email that they use on Facebook then within a day or two you'll start to see all of their friends from Facebook whom are also on Instagram in your recommended follows. All of this happens without email verification..

Yep, I have a relatively common name and @gmail.com address. Last week, some guy with my name signed up for Instagram with my email adddress and started posting without ever verifying his email.

I reset his password and tried to close the account after he kept trying to access it by resetting his password again. Instagram support asked me to send a clear photo of myself holding up some random number to prove it was me. Nope lol.

> All of this happens without email verification

This has very interesting consequences...

Whoa... so it was around in the open since around 2013, and still not fixed? 0_0

Almost every shop does this, no verification before use. ffs, at least provide a "report not mine" function.

I've only ever seen a "report not mine" function from Google. Where else have you seen it? I am not on FB/LinkedIn/most similar ones, so I may be missing examples.

You can even do a search by mobile number, by typing a mobile number into the search without pressing enter.

Depending on the owner's security settings, Facebook will often suggest the profile of the person in the type-aheaded search results.

I believe they removed this feature a couple of months ago.

Lucky you already have your account. These days you can sign up for one without a phone number, but then you flat-out can't sign in without giving one.

> The reason I never give fb my mobile

Here's the issue with it. You might not give it but your friends would. Therefore, this strategy is pretty useless as network effects kick in.

TIP which I discovered by accident: create a bogus account with your phone number.

Facebook will remove the phone number from your account when you do that. You can also use that to check who are your friend who gave FB your phone number.

> You can also use that to check who are your friend who gave FB your phone number.

Can you explain further how this will work?

Probably by suggesting users who have your number as friends.

this is an interesting idea but probably one already-implemented feature from being circumvented

Do people honestly give a shit about terms of service?

Yes. Especially ones with broad arbitration clauses, and double especially ones where your access to the courts is determined by whether you opt out within a short time period after agreeing to them.

These are frighteningly common, typically enforceable in the US even for consumers, and typically enforceable in most countries for even small business customers (though rarely for consumers in much of Canada and Europe if the vendor has enough ties to the area for local consumer protection law to apply and you win the race to the courthouse).