Hey Mike,
It is a perplexing issue. Of course the ILS's must "own" the keywords, and likely keyword purchase IS their highest operating expense.
The whole premise of the magazines and the ILS structure is to provide a value platform for the prospect renter to better and easier find a suitable apartment. And that whole function works best when everyone subscribes to that type of advertising/marketing, meaning the apartment operator, the ILS and the prospect.
So, which circles back to your original question, what happens when the savvy apartment marketer decides, finally, that it IS important to show up on a Google Search Ranking, and starts buying Adwords, they, by design are now competing with every ILS on Adwords and Google Page Ranking.
To me, this is no different than the early thinking by Search Engines (Pre-Google) that wanted to keep you on their site. Google comes along, and reinvents Search, literally, and wants to get folks off their site as quickly as possible, the point being the ILS's want the prospect to stay in their corral