Actually I honestly doubt anyone would bother. We're talking games and properties that aren't just old, they're part of brands that don't exist any more. Plus, if it is such a problem, ROM sites would all be dead by now.
Namco, Atari, Gottlieb/Mylstar, and Williams/Bally/Midway (now held by Warner, I think) actively enforce the rights on these old ROMs. Not as sure about Sega, Data East, Taito, and Konami.
I can confirm this; I've seen them shut down MAME arcades relatively recently (and with good reason... MAME arcade machines that actually collect money are dodgy.)
