Upvoted and followed. This seems to be a little on the "gray" side of things. For one, I'd ask myself "for what reason do I want an anonymous Steem account?" "What uses would I put it to?"
And, "Can this be abused?"
I can definitely see one method of abusing it, but it's not by the purchaser of these accounts: it's by the seller. The only way into the account is via the login; the purchaser doesn't have the email or mobile number associated with it, so cannot retrieve it if the seller decides to take the account over.
Which I can see as a possibility, because there's real money involved here.
The "SteemFacts" example seems innocuous and I've not been here long enough (3 weeks as of tomorrow!) to have absorbed all the ways accounts can be used, so it's entirely possible there's abuse risk on the purchaser's side, as well.
But with the threat of potentially losing everything I put into that account (whether in crypto, or in my time building it), I think I'll find other methods of creating separate accounts -- if I ever find the need to do so, that is.