The "+" feature of gmail is great, but I hesitate to use it after some weird validation problems I've had. I've stopped asking that people validate properly, and started hoping that they a) don't validate or b) fail gracefully.
One (very important) site properly validated my "+" email address on the front end (gave me no errors), but the backend failed and I never received the required confirmation email... all resulting in a customer service call. Arggg.
FYI this isn't a "feature of gmail". It's a feature of many, if not most mail systems (sendmail, postfix, qmail, etc.) and was around for many years before Google even existed.
Shouldn't the spammers have figured out the "+" feature by now? Just remove it and the suffix to get a valid address, for gmail or any other provider that uses the syntax.
I don't see this feature as a way to fight spam, but to make it easier to label incoming mail by using the sufixes. As you said, it's easy to bypass it with some simple find and replace.
One (very important) site properly validated my "+" email address on the front end (gave me no errors), but the backend failed and I never received the required confirmation email... all resulting in a customer service call. Arggg.