Good vs Bad Domains
Deciding to buy an expired domain can be a very savvy business decision. The possibility to research a domain's past to find out its history and popularity means that it is possible to buy an expired domain that has already had a significant amount of time and money invested into making it popular, and to do so at a cost significantly cheaper than the cost of registering a domain and then going through all of the work to push the domain up out of the depths of the search results to the top. That being said, there are lots of domains out there that have been bought and used for purposes that forever scar the domain name, causing it to be pushed down in search results or even removed entirely if a search engine associates the domain name with certain activity. It is impossible to do a bit of research.
What, exactly, makes a domain "good?" Well, if we're talking about popularity, then the domain could have any number of characteristics. Most important among these characteristics would be backlinks, PageRank, directory listings, and age. All of these factors are directly linked to how a search engine displays your page in the results. If a domain has a significant amount of equity in any of these fields, there's a strong chance that the domain will appear in a high position in search results.
Of these, the only ones that can have an actively negative effect on a page's popularity are backlinks and age. If a site has too many backlinks in a short amount of time it might be flagged as spam and pushed down; it is highly unlikely, however, that any domain not associated with spam would accumulate such a high number in a short amount of time. Age is sort of the opposite- the older a domain is, the more likely it is to appear higher in the search results. Spam sites are notorious for not surviving very long, so a domain that is relatively young is likely to be passed over in search results. These factors contribute to a domain being "bad." Obviously, if the factors are going to have a negative affect on the domain, you don't want to be associated with that domain. Domains that are associated with these types of web activity, as well as other types of SEO that are considered "spam," may never recover from the damage dealt to the domain's credibility.