Everyone in this thread is replying with instances of receiving emails meant for other people, but dots have nothing to do with that. It's people typing in the wrong email address in a signup page (with dots or without), and the service not verifying it. The latter is what really needs to be fixed.
I personally find this Gmail feature (as well as the ability to append +anything to your email address) extremely useful.
I personally find this Gmail feature (as well as the ability to append +anything to your email address) extremely useful.