No-one checks that the name on the boarding pass (which is trivial to manipulate before printing it at home) matches the name on the passenger manifest (i.e. the name in which the ticket was bought, which is where the checking against the no-fly list is done).
Actually, it is! When you present your printed-at-home boarding pass to the gate staff, they check that the name on the boarding pass matches the name on the manifest, and sometimes cross-checks when they scan the bar-code (if fitted), and then matches it to your photo ID. So don't worry, you can rest assured we're on top of it.
As for your old 'double wammy swap a boarding pass on an air-bridge trick', I'm much more worried about the quality of the Captain's crew meal as a threat to flight safety. Do you really want the cabin crew to check your ID at the door as well?
Hello sir, welcome on board, may I see your boarding pass and ID, please? Thank you, although this photo doesn't really look a lot like you, have you lost some hair? Well yes, that would be from all this stress we put you under when flying... Enjoy your flight.
