Perhaps he enjoys to drink some beers while playing blitz... losing a lot of games on a day is not so weird, because sometimes you are tired or listening to music, phoning and playing table tennis while playing a blitz game.
I think that losing on purpose is not legal. Losing to 600 is very strange even if you are high on drugs etc. ;-) I geuss you should contact an admin if you want him to be punished.
Cheers,
Jurjen
It would sure help to start by mentioning his nickname...
Putting off a win/loss to try and save rating isn't necessarily against the rules as it is unsportsmanlike and rude.
If you feel like he's doing something against the ToS then use the Report Abuse function at the bottom of the page and the staff will look into it.
Maybe he resigned from a tournament?
Firebrand:
I wouldn't say that's necessarily a sandbagger, it's a case of getting screwed by Glicko as it only factors K for the person with it sliding and not for the opponent. What I mean by that is that if you play a brand new 1200 and lose to them, instead of having no rating adjustment for you, it's adjusted like you lost to a 1200 instead of losing to an unknown entity. One of the many problems with Glicko. As an afterthought, with no ad hominem intended, how does a B player know what "tactics of an expert" are? 
I am playing a game of chess in a tournament. The first game against this player, his rating was around 1500, mine at about 1680. He pulled off an upset after I played poorly. So my rating went down some and his rating went up some. Great. The second game, his rating started at about 1550, mine at about 1660, and as the game has progressed, his rating has dropped dramatically. Right now, my rating is about 1630, his is about 1100, when literally 10 minutes ago, he was at 1300, and several hours ago, his rating was 1440. I have a feeling that he is sandbagging just to win back a ton of rating points as he is winning this second tournament game against me, and to kill my rating. I looked at his history, and he lost 8 games TODAY!! Several of them looked like either the opening or middlegame, and he RESIGNED AGAINST A 600 AFTER PINNING THE OPPONENT'S QUEEN TO THE KING!! Could someone please check and make sure that this is legal?? I'm sure that some of his losses and wins were real, but eight losses in ONE DAY!! That looks so artificial.