It's:

http://en.wikipedia.org/wiki/Nokia_N900#Known_Issues

"Nokia declines all such requests" is w/rt getting back the old N900 - the warranty makes it their property, so unsurprising, but the bolded bit is definitely wrong. The replacement doesn't come with a fresh warranty, either - it inherits the remaining warranty time of the device it replaces - as stated in the warranty text.

Honestly, I do despair sometimes at wikipedia.