I'll spare you the history lesson, almost. This is a link to a paper I wrote about Internet advertising in college, around Feb. '98. It's pretty bad, but it'll give you some history if you really want it. This topic has also been discussed here on K5 before, try here and here and here.
The SSP protocol is based on one of the fundamental properties of the Internet, the hyperlink. Unlike banner ads, pop-ups, and intersitials, SSP is both inconspicuous and bandwidth friendly. Ultimately the purpose is the same as any advertising, to grab your attention and move you to action. SSP is what originally brought me to this site, and has contributed mightily to the 40,000 unique vistors who have visited my homepage over the last year. It is both economically efficient and socially acceptable. In short, it is the future of advertising on the Internet.
SSP allows for pinpoint demographic and psychographic targeting using intelligent agents to maximize advertising potential. SSP also allows for the repetition much advertising need to be effective, again whle staying economical and socially sound.
In case you haven't guessed it yet, SSP stands for Shameless Self Promotion. You see it in .sigs, it exists in user profiles, sometimes it even gets submitted here as stories. In all senses, it is advertising, but because it becomes part of the conversation, it gains immediate street cred. The previous link to Cluetrain illustrates the protocol in one of its derivative forms, promotion for concepts, movements or products that the individual linking believes in. SSP is also compatible with the Cluetrain itself, as the manifesto mentions the immense potential of a linked workforce promoting the company in person, as a representative employee, while using the Internet at work.
As discussion sites gain popularity and more surfers are exposed to them, it might very well become the reality that careful use of SSP will be much more efficient from a resource management and overall effectiveness perspective. However, the downsides are obvious. The lowering of signal to noise ratios, fear and mistrust of fellow users, and of course, goatsex, are all immediately apparent. The general feeling of being manipulated is also one most humans find distasteful. But these objections and shortcomings are quite minor when compared with most alternatives. How much bandwidth have you wasted on banners you never see(none, eh?), how many pop-ups have you quickly clicked close, how many times have your actions and surfing habits been tracked?
In closing, I've seen and been using this protocol for a number of years, and wanted to give it a name. Promotion and advertising on the Internet are a simple battle for your attention. There is 1M times more "content" on the Net than any one person could ever consume. Getting someone to pay attention for your own will become an increasingly difficult battle, but it is a battle you can fight effectively as an army of one. Thanks to the SSP.
[final author's note: as per, I wasn't sure about the section, if your vote relies on such things, wait for it to be settled before clicking. This was also composed on the fly, so if it needs fleshing out for your +1, feel free to post why and where.]