The OP posted in 2010; the first reply is just a few days ago... 12 years later! There is a huge difference beteween what was availabe in WGT back then and what there is now. There were no coin games, all Scored or Ranked games counted towards your Score Average, which in turn determined your Tier. 5 Scored/Ranked games at Hack tier and you became an Amateur (the Score Average had to be below a certain figure, but you had to be incredibly bad to not move up at least from Hack!). 10 games at Amateur and you moved up to Pro. And so it went on and players moved up the tiers. Yes, even back then there were sandbaggers, cheats and multi-accounters as players protected their Score Average by either not playing Scored/Ranked rounds, or maxing out rounds so that their Score Average was hugely inflated.
However, with many players now just playing coin games, and with no apparent criteria for tiering up for those players, one can stay as a Hack with a 150 Score Average for a long time. I find it hard to believe that WGT look at every coin player to check how they are doing in order to move them up the tiers. I only ever play coin games now in Showdowns, but I still come across many players at Pro-Master tier who are at level 90+ and Score Averages that make them look like they haven't a clue how to play the game. The worst thing about it is that WGT don't care one iota so long as they are spending money, and as you can only buy balls with credits I guess many of these players do actually pay to play, unless they are doing free-credit offers. However, if they are only playing coin games, then quite frankly there's nothing to worry about because, as has been said many times, coins are both worthless and useless since you can't buy anything with them anyway, unlike credits which is what the OP was referring to with Matchplay Challenges. If you are worried about losing worthless coins then simply play in the cheaper coin rooms, or better still not at all!