Therein lies the problem...If WGT is relying on its members to enforce multi-accounting by emailing them on a one-off basis everytime they suspect someone is MAing...what do you think you would have in terms of an effective solution?
Not only will they be inundated with emails, it will take them twice as long to sort through all the ones that deserve attention.
While it maybe against the TOS for WGT, I would still argue that outing members in a public forum is the easiest, cheapest and most effective deterrent. This combined with some technical resources, and I think WGT could more or less solve a problem that will only continue to get worse. Obviously there has to be some guidelines, or else the slandering would be a problem worse than the MAing.
These are just thoughts, but there are some respected members of the community who might not mind taking on an advisory role. If a player strongly suspects someone else of MAing, there could some check points for them to go through before posting, and the member advisor would oversee it to make sure it had merit. Like I said, just thoughts, but this is definitely something that needs to get sorted out before the game hits the mass appeal it is headed towards.
The forums are the best place to foster discussion, and also get the attention of WGT...just take a look at the recent Ready Go payout thread, where there were some outstanding posts that I believe went a long way in having them change a broken payout system.