I'm obviously biased by visiting HN, but buying any computer used that has not been wiped is a sure indication that it is stolen. I'd like to give the guy the benefit of the doubt as well, but there is ample indication in this article alone that he either has no clue about technology and the responsibility of buying one used or was the one that stole it.

If it turns out he bought it legitimately without knowledge of it being stolen that's fine, but he still should have been turned on to the fact it's filled with someone else's crap and the username is not his. Ignorance is no excuse, even though it may be commonplace.