It isn't possible for the accounts michael.laccetti@gma.. and michaellaccetti@gma.. to belong to different users, as far as Google is concerned it's the same user.
You can also use the +subscript feature for that. youremail+twitter1@gmail.com youremail+twitter2@gmail.com. Allows you to filter based on account as well.
Except it's still distressingly common for braindead email address validation scripts to not accept the plus character.
So, I'll use the plus to sign up for something that may produce junk (to differentiate it), and then attempt to unsubscribe--producing an error as the web form email validation to unsubscribe doesn't accept the plus. Doh!