This has been a huge debate on the forums here lately. I am going to assume a lot of it has come from Champions using both, but there are a lot of popular RMT games we have been showing ads and running contests for. Fiesta Online has seen a gain in consumers due to ads here and other games as well.
I personally have a lot of problems with the RMT model. On paper, this is an awesome idea. You let people play your game for free, but you make them pay for in-game items to support profit vs cost. It is a business model that is working out very well for a lot of companies. My first experiences with this model was Gunbound YEARS ago. I will admit that I spent quite a bit of money on that RMT MMO without knowing what I was doing at the time.
With my experiences of both, I have seen the best and worst come out of each experience. I personally have a hard time listening to someone say that RMT is healthy for ANY game. My reason is very simple. You are required to "BUY" the best gear in the game. I know this isn't true for all, but for most it is. The end game of these FREE mmos is sololy based on who has the most "REAL" money. Skills almost become useless. Someone can buy their way out. The only time skills come into play is when two players both spent uber amounts of money on their characters.
This is where the business model fails for me. I don't mind paying 15 dollars month for a video game. I completely understand and agree with where the money is going PLUS everyone gets a fair advantage for the most part. The RMT model is a completely different story.
I realize that some of my points are not true with ALL of these types of games, but they are for most. Free MMOs are always going to be supported because they are FREE. You can't beat that. I personally have very little interest in them. I did enjoy Fiesta for a short time. They are nice to have when you are burned out on your current MMOs, but I could never see myself getting to the end game of any of these types of games.