Most peoples' aversion to advertising ends the second they have to pay cash instead. Basing a business on advertising is a rational response. Remember the incredible tantrum on HN when Chargify started charging money?

As for the free users, well, fuck them. Nobody owes them free services or software. The implicit contract with someone providing you something for free is that they're monetizing you and your interaction with their service some other way. (My new favorite quotes: [1])

[1] http://blog.earlh.com/index.php/2012/06/two-quotes-about-the...

edit: @eykanal: I meant fuck the free users whining about advertising.