In the uproar over the EVE monocalypse, CCP's CEO Hilmir Petursson foolishly said something very true but hurtful: "I can tell you that this is one of the moments where we look at what our players do and less of what they say". The true measure of acceptance of microtransactions in online game is not how much people complain about it, but how many of them actually pay.
The percentage of users who pay varies a lot from game to game. Zynga with their Facebook game is said to "convert" only 1 to 3 percent of their users to paying users. Free2Play MMORPGs usually cite numbers in the 5 to 10 percent conversion range. One of the best ratios of paying users to overall users is from World of Tanks, 25 to 30 percent.
I would argue that this is because the microtransaction model of World of Tanks is the most fair. I once called it a payslope instead of a paywall: The further you progress in the game, the more are you encouraged to pay. That isn't to say that it is impossible to directly buy a big tank and gold ammo, but the investment would be a bad one, as you'd just horribly lose all the time. Even for experienced players using gold ammo in a random battle is kind of a waste. Only in the "endgame" of clan warfare where every little advantage counts does gold ammo make really sense. And then we are in a situation where those who play most and most intensively also have the best motivation to pay. That sounds rather fair to me. And seeing the conversion rates, it apparently sounds rather fair to many players.
Now that I'm trying out iOS games, I notice that many of these have a similar basic philosophy: Many games exist in a free "lite" version, and only if you play this for a while, like it, and want more, do you pay for the full version. That's a one-time purchase in most cases, but the principle remains the same: Those most interested in the game pay.
Many of the "DotA" or "MOBA" multiplayer online games also have widely hailed payment models in which everybody can play for free, and payments make most sense for players who play intensively. That this works best is logical: The more you like a game and spend time with it, the easier it is to persuade you to pay something for it. The n00b who never played the game and directly spends hundreds of dollars on it on the first day is an urban myth.