I wonder what the economic impact on some smaller companies would be if anyone decided to really come down hard on the kind of sites you mention. If roms were extremely hard to come by, would there still be as much demand for products made by GroovyGameGear or Ultimarc? I'm sure they would still get business, but I imagine that it probably wouldn't be anywhere near as much. The whole retro gaming solution would probably be a lot smaller than it is now.
Just a thought.
I think there's a fine line with the topic of Rom's.
Mame has been funded through donations from a group of fairly highly technical users, without their support, Mame likely wouldn't have advanced nearly as far as it has due to funding restrictions.
Companies have, in the past, found value in Mame's code, either as a reference or a template, for their own rereleases of arcade packs.
I strongly suspect that so long as Mame remains in the domain of a group of fairly highly technical users who would be considered small by market standards, that at least some companies are content to ignore Rom distribution in favor of benefits from Mamedev's work in reducing time to market of their own arcade packs, which likely sell to a much larger market.
What I mean is, theoretically, Microsoft could use Mame's codebase to rapidly build a library of arcade games on Live, and sell people the roms. I doubt Microsoft cares about a couple thousand Mamers in contrast to the millions of X-boxers they can sell to, and they know they'll do better releasing more classics faster.
So I strongly suspect that any niche distribution will go overlooked as long as Mame remains a product that isn't accessible to the average user. Especially since I'd imagine that all of the companies in question have some significant percentage of employees who themselves are fans of emulation of old systems.
Lets be honest, all of the companies in question know about Mame, and it's distribution methods. They are software companies, they have computer scientists and software engineers everywhere, who generally are well aware of emulation. If they were going to make any major push, they already would have.