Seeing all the Chinese manufacturer spam posts coming in on the RSS reader. I think spammers pushed people to services like Facebook by being a bot bullies with unsolicited off topic posts. Email registration is the problem. Not unique enough. Some services now require a phone number and two factor authentication by inputting a number received by text. Others require authentication by a service who uses this like Facebook or Google sign on.
An additional task in management of an online forum that makes life not as fun, time consuming and off topic. Maybe there is a phone number registration mod?