I'm not too sure about the recent case, we'll have to wait and see the result of the investigation.
I think the only time anyone has been found guilty of match-fixing was Peter Francisco, a South African player in the 1995 World Championships. There was an inordinate amount of money placed on a 10-2 scoreline to Jimmy White, which ended up being the case.
Francisco was banned for 5 years, I think, long enough that he wouldn't have any chance of coming back at that stage of his career.
Another instance that I'm sure you'll be aware of is the ban on Quinten Hann, though I think there's only evidence of him talking about it and no examples in matches.
In more recent years there have been a couple of allegations over the results of matches in the group stages of the Grand Prix and Malta Cup, and even an accusation of former World Champion Peter Ebdon, though nothing ever came of these.
Overall I think snooker is a pretty clean game, though badly run and lacking money for those in the lower ranks. For a few disillusioned players who aren't making a good living from the game then maybe the incentive is there, but for most the game is their career, they put in a lot of work at it and they would have to be in a very desperate situation to take such a big risk.