Google Webmaster Tools just released another video about buying a spam domain with Matt Cutts. I think this is a good question and is something that people who are interested in buying any domain name from a private party should be aware before buying.
Here is the question that Matt Cutts answers in the video;
Can I buy a domain name on the secondary market that has a lot of spam on it and still rank? How can I reset the SEO of that domain ? Thousands of root domains coming from spam.
Johan Tavard, Hua Hin, Thailand
In my opinion you should NEVER BUY any domain name that you know has previously been used for spamming purposes. “You don't want to be the person left holding the bag” commented Matt Cutts in the video. That is a pretty good analogy as you would have a lot of work to do get the domain off of Googles blacklisted domain list and not be recognized as a spam domain.
You can submit a reconsideration request to Google if you have purposefully (most of the the time people buy domains not knowing) bought a spam domain. Cutts mentions in the video though it would be kind of a pain to take and document everything so can Google take a reconsideration request seriously from it's long list of blacklisted domains. (If your current domain name has been marked as spam domain you can also file a Google reconsideration request.)
If Johan could get the spam domain in question for free, then I wouldn't see a problem with it. He would have a lot of work to do though. In the video Matt Cutts mentions that the domain in question Johan is interested in purchasing is $5,000 dollars! I wonder what drugs that blackhat spammer was taking when he quoted that price?
I personally would never buy a domain that has been blacklisted, let alone one for that amount of money. If you register a brand new domain name you are starting at the ground floor and it is easier to work to make the domain and site into what you want. (Of course it is still a pain to get ranked and have good SEO on any site.) Cutts says, “When you start out you are already in that hole” meaning it is going to be hard and a lot of work to get the domain unmarked from being a spam domain.
If you are really interested in the domain that has been used for spamming, I would recommend just waiting until the spammer drops the domain name. Once it gets dropped and you can hand-register it Google will no longer be on Google's blacklisted domain list.
Anytime your purchase domain names on the secondary market from well-known company or private seller it always a good idea to check the DNS Blacklist to see if any of them are blacklisted domains.