The OP reminds me of O'Reillys 2003 piece (buy where you shop) http://tim.oreilly.com/articles/buy_where_shop.html

In his piece Tim OReilly warned against people who browsed at bookstores, but only shopped online.

I suspect the same is true here.. if you use $service regularly, and $service exists through advertising, then maybe whitelisting their ads is a reasonable trade-off to make..