DX has some good items, some crappy. I've never heard of them damaging stuff, but it's always a possibility with these very cheap chargers. Just check the reviews - it's pretty easy to sort the decent stuff from the junk on there. And if there are no reviews, just skip it. They have 10 versions of *everything* on their site. A tip - when searching, use the "new beta" graphical search. Then sort by popularity. Then just ignore the ones with no / low ratings. That'll get you to the better items quickest.
It takes hours just to browse that site, and I'm sad to say I've spent 100's there on "cheap" stuff. I love it.
I can't wait till they get knock-off docks for the Vibrant, the $50 OEM ones are a bit steep.