Re: I've seen a definite uptick in these
"You could always blacklist anything not containing one I suppose, but would need to be pretty disciplined about it."
That's what things like mailfilter are for.
To clarify, I was thinking about discipline in only handing out sub-addressed addresses and refusing to accept mails not including them. Becomes more difficult when giving your email in person or dealing with sites with broken mail validators. As soon as you start accepting some without the sub-address you are back to having to look at them at least some of the time to figure out if you need to update your whitelist.