I would guess few (censored by writer him self) players who take eternally long to make a single turn, supposedly hoping you leave before them.
This is a really annoying thing in this game, not to say THE annoying thing. (Besides people playing to win in the training room.)
Fluffwig is correct
low star count deck, fast connection, and some bit of luck.
reading the game rules help me alot. heres a link: http://www.urban-rivals.com/gamerules.php?show=table
its easy to break the 500 points barrier if you just read and understand this simple rules
670 ? Geez... the highest I got so far was around 580. I am playing a deck with 3 and 2 star cards which is capable of wining all 4 fights in a match as well as going into KO with pillz left. I usually get around 25-35 points a match.
But sometimes it seems like ppl are getting ~50 points a match and I don't know how. The only explanation I have for that is that they might have help from guildmates. Playing a full 1 star deck against a full 5 star deck in the Danger Zone to make sure the low levels win should give you tons of battle points, especially if you think about level up bonusses and probably the KO bonus. Do that twice against the same guy and then probably against another guy from your guild and you have a very solid position. Plus, guildmates play as fast as possible too.
However, to make it clear, this is only what I can think of to get to 670. I am not accusing anyone of anything especially since I know first hand you can get to ~600 points without any help at all.