I've played a lot of games, and when I lose a game of Dota it's absolutely devastating but when I win a good/close game, I am absolutely euphoric, sometimes even into the next day. I don't think (most) people actually take the game very seriously, it just has to do with the mechanics involved. First, it requires a high level of knowledge and focus. There are constant macro and micro strategy decisions to be made and a high level of constant fine motor skills required. Additionally, you are highly dependent on your teammates, as they are on you. If one person on your team makes a big mistake, it can cost your team the game. However, there is frequent opportunity to work with your teammates to set up great plays, which are extremely rewarding to pull off successfully. The third important factor is the match structure. Each game of LoL/Dota is a discrete thing with a small number of participants. It is common in other multiplayer games today to have people coming in and out during a "session". For instance in first person shooters, perhaps you join a 32 player server that is halfway through a map, you play for 15 minutes and then the server changes maps. New people join, some people leave. In LoL/Dota, a game lasts 30-60 minutes and you are stuck with the 5v5 team for that game. I think the extreme highs and lows are at least partially due to the above factors: the level of focus required, the intense team dependence, and the match structure.

> I'm getting the sense that the real cause of the issue is that for some reason people take Dota way too seriously. If you lose, what's the big deal? You still had fun right?

When you start getting better in such games, you need to be very concentrated, very nervous. It isn't all fun and casual gaming anymore. When this concentration pays off and you win, it feel amazing, when it doesn't and you lose, you feel miserable. Anyway, you can't get back to lower level casual gaming (make a new account, for example) since it becomes so easy that you could play blindfolded.

Of course you could somewhat alleviate the negative effect of losses by having good permanent teammates, also whole game becomes much more interesting if you coordinate with fellows you know. Still, blame shifting happens even in the friendliest of teams.

I've stopped playing MOBA (HoN is my poison of choice) when I understood how nervous and unpleasant I am after the game session.

what some people don't realise is that MOBAs - played at a high level- aren't a game anymore, they're an e-sport. They are played competitively, the only goal being to win. This applies to HON/DOTA/LOL, but also to Counter-strike, Starcraft, and, to a certain extent, Halo. Obviously also to Quake and UT, but those are to old to be relevant now. An e-sport is taken as seriously as competitive sport in the USA. Any American will know how important winning is in sports. To understand the importance people attribute to winning in some video games, you have to see them as an e-sport.