Quoted from anathematize:
I'd wager a trivial amount of actual sales come from the 'targeted' marketplace ads on this silly website about a game that interests middle-aged white men.
Its downright amazing the amount of time and energy people are wasting on such a nonsensical issue.
On the flip side - for some people making mods is their livelihood, so them being able to feature prominently is important and could make the difference between being able to pay the bills one month and not.
If the ads system is monopolised by entities with the power to do so, either through sponsorship or abuse of the game linking system then all it means is people lose faith in this part of the website, their eyes will glaze over when they see the shop section of whatever game they're interested, and that's that. When was the last time you looked at anything on Google beyond page 2 or 3?
One quick and dirty solution I can think of is a weighting system whereby the more games a mod is linked to the less prominently it appears in the list. This makes sense if it's a generic mod anyway, as it's more likely people would be familiar with it vand aware of the global compatibility anyway (e.g. like PDI glass or ColorDMD). This weighting would mean a mod that only exists for one or two games would always feature highly relative to one-size-fits-all mods.