Rooting is cool. I root my phones. But when I sell or give I never root it. I put it back on stock. If something happens they can get it worked on through the normal channels (calling tech support or the carrier). If I root it I become tech support. Not cool.
Case in point. Someone I knew had a Samsung Factor. They were very sad that they had a Transform Ultra but left it on the bus and now it is gone... So I thought I'd help them out. I flashed a Samsung Epic 4g (non touch with the keyboard) over to Boost and gave it to them. I told them I'll help them through activating it on the network. But they are smarter than me. They tried to do it themselves. Now the phone will not activate. They are upset and I'm out of the phone plus shipping (they live in another state). Will they send the phone back? I dont know.