Tyron Ball, one of the young guns of the website buying and selling on the SearchForecast marketplace has provided a very good segmentation of buyers and sellers of websites and domain names:
The Industry Operator: Owned by a business/professional within their industry – as per dentist being owned by an actual dentist. In many cases this person is just forwarding the domain into their corporate website. Have probably had the domain for many years. Good chance they have already been approached by people wanting to buy their domains.
The Capitalist: Someone who has set up a website on a good domain, served some Google ads and bs content. Usually a bit of a tech geek / online marketing guy. Probably has some view of what their domain is worth – no doubt much higher than its actual value.
The Lucky Opportunist: Someone who managed to register a great domain name early on and has no idea what to do with it but knows they have something of value.
The Savvy Domainer: e.g. Dark Blue Sea. Usually an ads portal site. Going to want a lot for the domain if they even want to sell it at all.