I have had a very rocky ride with a certain merchant over this very issue, and only the threat of "outing" them on the web has convinced them to reimburse me the commissions that they cancelled from my account. They also terminated my account without notice and the whole thing left a very bad taste. This was no small deal - I was generating around £1.2 million per month for them and they were clearly happy with the traffic.
I should point out that it was not a
TD thing, but thought that this was very much on topic for this thread.
However, the real culprit here was Google Adwords, who will happily suggest competitor brands as keywords and allow the ads containing those words to run within minutes, with no editorial review. Overture, Espotting and the others all throw out competitor brands.
Having been bitten quite hard by this, I now make a point of asking about keyword restrictions before setting up a campaign, and would advise others to do the same.
Fortunately, the net result is that I have used the situation to leverage another merchant in the same market to increase their payout to match the "banned" merchant's offer, but I still feel that it's a worthwhile cautionary tale for any newbies.