Yes and no, Ari. At the beginning, people would register names that they thought big companies would pay big bucks for, i.e. cosmopolitan (for the mag...who refused to buy it!
They went instead with cosmomag.com
), target, unitedairlines, stuff like that. Lots of them did cash in.
Although there are unlimited possibilities online, many of the good ones are starting to be taken. Smart developers buy a name that has good potential and develop the site/forum, get the page rank and search engine optimization up, get it listed in the search engines, and then sell it to someone who wants a ready-made site. You can make good money doing that.
BUT, $20,000 for a good domain that isn't already a licensed name for an established business is highway robbery!