So being as how the bootload is locked, does rooting actually void the warranty? When I had my Nexus One, it was the act of unlocking the bootloader that voided the warranty.
I don't see anything in the warranty that say rooting or loading different OS voids the warranty.
https://motorola-global-portal.custhelp.com/app/answers/detail/a_id/48614
http://cache.vzw.com/multimedia/mim/mot_droid_x/droidx.pdf
This falls under the stature of modifying of device software without permission... I don't remember the exact wording and location but this is included in any and all contracts related to the electronic industry.
"Unauthorized Service or Modification. Defects or damages resulting from service, testing, adjustment, installation, maintenance, alteration, or modification in any way by someone other than Motorola, or its authorized service centers, are excluded from coverage."
I guess this would be the catch all.
I'd un-root, but I honestly think you could send one back fully rooted and ROM'd, and nobody would notice or care. My guess is, they pile all the returned phones in similar model piles and have some re-tard wipe the phone with the latest sbf. If it starts back up, they put through a series of standardized test, gets a new skin and goes to packaging for refurb shipments. About 60 days after a phone hits the stores, they only care about whatever model is coming out next.
I have never restored to stock, I have sent back blackberries, an OG droid or 2 and a couple of Dxs with what ever was on them and never heard anything. Sometimes I had no choice because problems with the phone prevented it.