From a SEO standpoint, web admins may (should?) want to apply the rel=“nofollow” attribute to outbound link ads that have been purchased and placed on their sites.

Failure to do this may cause Google to reduce the ‘trust’ level of the your site having the paid outbound links. See: http://www.mattcutts.com/blog/text-links-and-pagerank/ for an explanation of why Google and other search engines may penalize your site for failing to differentiate between editorial (natural) and paid links.

Search engines like Google judge the quality of your site based partially on your outbound links, and in order to avoid penalties, they want you to differentiate between “editorial votes” (natural linking) and purchased links – and the way to do that is by applying the rel=nofollow attribute to the purchased outbound links.

As of right now, the only way to do this in the textlinkads module is to hand-modify the theme_textlinkads_ads() function, or supply a theme-specific replacement for the non-trivial theme_textlinkads_ads() function. If you have multiple sites, this can be quite tedious and error-prone.

I propose that we add a settings option (checkbox) that allows the site admin to specify whether or not to apply rel=nofollow to all TLA links, and that option should be enabled by default.