Not sure about everyone else, but my problem is that it shapes game design. Everything from quest design, difficulty, balance, etc... begins to drive the games progression and development. Risk vs Reward gets skewed by the concept of selling favors.
I agree with this.
Games with "microtransaction" systems are designed from inception for there to be some sort of annoying / in-your-face mechanism that can be bypassed via payment.
For example, the energy mechanism in "free-to-play" games (pay as you go I think would be a better term) is designed from inception to encourage players to buy more energy when they run out to do stuff. Usually games that use this (or some variation of it) are designed to allow a player to do a few things and then run out of energy. Energy returns slowly - usually tied directly to real time. Then the game allows you to buy energy to bypass the wait. Games that use this are designed around making the wait tedious with the actual 'gameplay' being relatively fast paced to encourage the purchase of energy.
The end result: the game is designed around payment and, if that is the case, I'd rather just pay up front and not get dollared to death by some microtransaction shop. These games are also designed around whales - that small percentage of players who will spend a fortune on the game because they become addicted to it. According to Zygna (King has also released similar statistics) less than 5% of their free to play players actually pay up. Further, whales are a minority within that 5% but they spend a ton of money. Other free to play companies have noted similar trends that a very small percentage of their userbase will pay.
That's why free-to-play games need to have a lot of people playing them to make money. To put it into perspective, if a game has 100,000 people playing it less than 5,000 will participate in purchases from micro-transactions. But, happily, from that 5,000 people there will be a few who will spend a small fortune on the game.
To me that's why free-to-play is a lot easier for web games since they are incredible accessible and allow for millions of players. From those millions will be tens of thousands to hundreds of thousands of actual paying customers.
Now think about MMOs - how many MMOs have maintained over a million players over the long time? That's how many would be needed to provide the same revenue as 50,000 to 100,000 subscribers paying full price. I imagine there is some flex in those numbers since over time the people who wouldn't pay likely stop playing entirely leaving the game full of, for all intents and purposes, paying customers. The question then becomes how much are these paying customers spending? Are they spending, on average, more than $15 USD a month?