How much do you think your WoW account is worth? $200? $500? Maybe even $1000? If you head over to Ebay, you will see thousands of WoW accounts for sale. I figured out that my AQ40 geared priest and Tier 2 geared warlock, along with various alts and several thousand in gold, is worth approximately $700-$900. I didn't do the exact math, but the time spent leveling all the characters and gathering all that gold and loot...well...let's just say that the new guy working at McDonald's makes a lot more per hour than I'd generate if I sold my account.
That said, if a person was totally finished with WoW, never to return to Azeroth again, why wouldn't they at least consider selling their account? Granted, the return on your time would be bad, but it is better than the zero return you would generate if you never sold it. On the downside, I could see account selling being a popular target for scams, and it is, afterall, against the Terms of Service, so you could expect no help from Blizzard if something goes awry.
Personally, I don't think I could ever sell my account, as I have a lame emotional attachment to my characters. I just can't imagine some stranger playing my characters I worked so hard on.
What do you folks think? Is account selling on the same level as gold buying? Would you do it?