A couple of weeks ago, I got a PR-blast email offering up an interview opportunity with the CEO of SocialMedia Networks. Just another Web advertising middleman, but with a twist: It’s exclusively targeting the Facebooks and MySpaces of the online world.

I didn’t take the bait, partly because I knew someone else would.

Ads on social network sites aren’t new, although far-reaching monetization attempts have met resistance. Marketers follow the eyeballs, and when more and more people spend more and more Web time on these dedicated sites, that’s where the money will go.

But how effective will these ad pitches be? Operating on the premise that a website is just another website might not work in these settings, because something like MySpace is tacitly considered a no-sell zone. That doesn’t mean it won’t yield responses, but those will probably be accompanied by higher-than-normal instances of backlash.

In a sense, blogging marketer Paul Chaney probably best characterizes this approach thusly:

Advertising on social media sites like Facebook, Bebo and others is akin to going to a restaurant and asking for a seat at someone else’s table. Maybe they’ll be receptive and maybe they won’t. Conversely, to create your own branded socnet is to invite others to have a seat at your table.

It’s all context. That’s why I always felt that all those commercial presences via MySpace/Facebook pages — promoting movies, consumer products and even rock bands — are odd fits. If a social network’s purpose is to foster person-to-person connections, how is someone supposed to credibly claim a “relationship” with a marketing piece?

Conversely, I don’t agree with the call for advertisers to create their own dedicated, branded site just for a MySpace-like experience — that’s a lot of heavy lifting for a campaign which might or might not have a short shelf-life. I guess that opens up an opportunity for a third party to offer up a middle-ground solution: Cookie-cutter social-network setups that can be developed for single-purpose messaging campaigns and that can be ramped up quickly.