We have some TM domains that we purchased for the same reason. Not to violate any trademark, but to promote the company, to be used by dealerships or local outlets. Seemed like a good idea for the TM company to let their stores promote the merchandise.
The thing is, there are cybersquatters who set up websites hoping to syphon off traffic from the TM company, and of course they take a dim view of this since it doesn't help the company and could dilute the mark. This will get their attention for sure.
On the other hand, if the TM company is bothered by you simply owning it, they will let you know. Then you will have to turn it over, most likely. If they are parked on some pay-per-click directory it may cause a little problem.
Just owning the domain isn't the big problem. Sedo and Afternic have hundreds of TM domains for sale, so the general idea of selling the TM domains doesn't seem to be an issue that is worth pursuing for them.
I'm not an attorney, not a cybersquatter, and don't condone infringing or diluting TMs. Just sharing our experience on the matter. Hope it is helpful or somehow enlightening.
