Not used text ads, but using RSS feeds to add content from other sites has certainly had an SEO effect on a site I've been working on.

Similar idea I guess, you get some words on the page that may not usually appear, and in this case all I'm using is some news headlines.

I'm finding that we're getting SE referrals for terms that combine words used on the site anyway, and words used in the RSS feeds when the sites been crawled. It's a bit random as the headlines are changing all day everyday, so it's pot luck what's there when the spiders crawl.

In the case I'm thinking of, it's not actually helping drive targetted traffic, but with a different site/feeds it certainly could.

I'd be interested to know how you've been getting on with this, I'm thinking of giving them a whirl myself just from a money - making perspective.

SEO wise....I might try what Adrian just mentioned... I allow my RSS feed to be used on other sites and that has been a decent traffic generator, never considered the benefit of adding other peoples content though.