MTs are a basis of funds that allow such competitions, which in turn funds advertising/marketing which ultimately grows the user base and generates more money. Repeat.
They're a good thing if -and only if- basic gameplay is not restricted, with MTx's being necessary to unlock the core game.
If MTx's are for additional content, like demos, guides, skins etc, then it does no one any harm since it's opt in; your own choice.
This is all superseded by how the founding company uses the income from MTx's of course. If they line their own pockets the game will hit a plateau. If they push it back to the community (as we see in the DOTA2 thread) it can generate insane popularity and growth.
That's true, but the number of Dota 2 and League players counters that point, proving that the publisher's support and payment model are very important.
If salaries were included I think the list would be dominated by SC:BW, which would again prove that impressive & interesting to watch games have their advantages, too.