[dividedbyzero]

It's a bad idea because URLs, email addresses and user names help with phishing, identity theft, social engineering, matching with other leaks, may lend themselves to blackmail (certain dating apps) or otherwise endanger people (gay dating apps in certain places), for very questionable benefit. No definite idea if they really do that, but if they did, that would strike me as irresponsible.

Also, I think the failure here is to not use cryptographical methods in the first place which would seem to be a screw-up in a different security specialty.