Question about cheating

Is it cheating when someone deliberately loses a (rated) game? I just saw a game 2200 against 1200, where the 2200 player blundered all his pieces and then resigned. At one move he played a6, attacking the white queen on b5, the 1200 player didn't react, but the 2200 player refused to take it. Shall we report such games? Will this be taken seriously?

Yes. That's sandbagging, a form of cheating.

http://en.lichess.org/qa/258/all-about-cheating-questions-and-answers < more info

A note: blundering pieces is sandbagging, however, simply choosing not to capture a piece is not cheating, even if it's obviously the right move.

Thank you for the quick answer, although I have difficulties in seeing the difference in #3.
Will this be punished as hard as using an engine? Can a player be marked as a cheater because of this sandbagging?

*opening Books*are allowed in Correspondence games. Just books. Just for the opening.

Cheaters are treated equally: be he an engine user or sandbagged (or both), he'll get a (or two) labels marking him accordingly.

So another cheater is reported, let's see how long it will take this time. Of course you were right, he is using an engine and sandbagging. That's the way a lot of cheaters do it here. What a great strategy to avoid beeing detected!

I understand the concept of "sandbagging" from a golf perspective (i.e. by making your handicap rating make you appear to be a less strong player than you actually are, which you can later exploit to win matches and money when it suits you).
In pool, people who sandbagged would sometimes would get their thumbs broken when they screwed-over the wrong opponent at the wrong time.

But, I don't get how sandbagging helps a player in chess?
What's the motive? The payoff?

Also, if a "2200" player keeps losing to "1200" players, they don't remain a "2200" player for long.
I'm not being deliberately obtuse :) I just don't get it.

It's good to ask if you don't understand :)
Sandbagging is lowering your rating deliberately. Then, by playing a higher rated player (like those found in the tournaments), they are able to beat them and, because of a low rating, are awarded many more points (and their opponent loses many more points than s/he should have).

Obviously, you'd be displeased if you lost 30 points to a low rate player.

It's also an issue if there are tournaments for certain rating ranges. Like if there's a tournament for 1200-1400 rating, and a 2200 rating player joins with a false rating of 1300... That's completely unfair.

It doesn't help the sandbagging player (it could help their opponent boost their rating) because the goal is to damage others' rating (or just to feel good for beating a "higher ranked" player than them).

Here are many players who deliberately lose games, because they play all there winning games with an engine. If they played really all there games with engine, their rating would increase so rapidly, I guess they would be detected very soon. But this way the process takes longer and also people may think, if this player loses some games, this won't be a cheater. I think these are the main reasons here.