I fully support the "free app with ads" and "same app, but pay to remove ads". Either way, the developers get money for their time.
However, games that are "free now, pay forever" or "pay2win" suck.
I think the very first game I ever saw pay2win was Farmville with their FV dollars or whatever. My already poor mother in law was completely obsessed and had dozens of Facebook accounts all farming at once. As soon as she would get her gov't check, she would blow the whole thing on FV dollars to buy the best decorations or crops.
Currently, my daughter is playing My Little Pony which is identical to Farmville, except with the cast of MLP. The worst part is that the vast majority of desirable pony characters (from the show) can only be bought with gems... which can only be bought with, you guessed it, real life dollars. When I asked her what she wanted for Christmas, the only thing she wants are those pay2win pony characters.