In case the previous 163 comments didn't make the suggestion, here's an easy way to get rid of lots of impersonators: anytime someone opens a new account with an image, run an automated comparison to all existing profile images.

If it matches one of those, especially if it's one with many followers, it's most likely a spammer trying to impersonate existing members with large followings.

At that point, you can refuse to open the new account. Better yet, be a little sneaky - let them open the new account and pay the membership fee. Once they do, as soon as they try to post an article or a comment, require them to change the image and the name readers see to ones that don't replicate existing ones.

If it was a mistake (as unlikely as it may seem), they'll make the change. If it's a spammer, they'll likely abandon the account, leaving the extra $5 or $50 to be distributed to legit writers...