That's dumb question, probably won't accept the guy due to the site already has an account... try at least.
FYI... Read here >> http://forums.digitalpoint.com/faq.php?faq=revenue_sharing This means multiple Adsense publisher ID's are used for this one forum. If the publisher ID of a revenue share member here gets banned, it doesn't harm DigitalPoint's account.
I want to echo some of the other comments here - remove the ads before you sell the site. I have just given away one of my sites (yes I know I am crazy) and took all the ads off before I let them have it. Not worth the risk.
Making stuff up as he goes along? you are wrong! a site can have 2 different ad codes, just not on the same page.
If he/she buy your ws,he/she will put his/her own adsense on that ws,otherwise you will get the cheque.
Many of us are using our AdSense id on this forum, which is of course not our site. So I don't see a problem keeping yours while applying for a new one.
An Adsense acccount is not tied to a specific website and one website can share multiple Adsense accounts as DP does here.
There is no harm in keeping your ads running on the site as this will give you earnings as one site can share multiple ad sense id as we are using it in DP. So, it's up to you if you want to earn from the site then it's k otherwise you can remove it.
Its better you remove it. You dont want to see a mail from adsense saying your account was found to be related to an account previously banned etc etc.