What an interesting question! As it turns out, I have recently purchased links off two of these sort of novelty or gimmick marketing sites, Joel Comm's 500words.com and Randy Cassingham's 1024ads.com. Each was approximately $100 for a link that will be up and online for at least a year or two, if not longer, and to be candid, both are good friends and I like to support their entrepreneurial efforts, however wacky.

However, was it a good advertising investment versus, say, putting $100 into a savvy, targeted AdWords campaign? Probably not, to be honest. Buying a link on one of these sites is clearly a gamble, a bet that they'll get sufficient visibility to really turn that cheapo link into a meaningful traffic generator.

To get more insight, I asked my friend Jim Kukral, who just launched a blog called Million Marketing Blog.com that's focused on just these sort of flash-in-the-pan phenomenons, to share his reaction to your question. here's what Jim says:

"Like visiting a flea market, you have to pick out the good investments from the bad. The same goes with viral media projects. Basically, viral media projects are built by online entrepreneurs who are hoping that they can create a clever and unique Internet idea will get the attention of both buyers, and readers. The buyers are needed to help fund the project. This can take the form of buying pixels, or words, or even footsteps! The readers are key because they are the ones who supply the viral aspect, by talking about the site and sending it to friends etc...

"A buyer can expect benefits like extra website traffic, possible search engine ranking benefits, and general marketing presence. So for example you could buy a "word" and link the word to your website. So any reader that visits the project might see your word and click on it to see who bought it. This could in turn turn out to be a customer or new subscriber to your online business. The benefits to the buyer are greatly associated with the popularity of the project. So it's often best to look at how the project is being promoted, and by who, as a good indication of how popular it will be. The most popular ones will bring the most return!"

I hope that our collective commentary will help you figure out which of these virally transmitted gimmick marketing sites are worth watching, exploring and joining. Good luck!