First, the Google link: command only shows a subset of links, and usually only the best quality links. If that is what you are using, I'd suggest you look at the Yahoo linkdomain: command results, and also sign up for Google Webmaster tools and look at the link lists within that tool -- those are much more comprehensive and accurate than the Google link: command.

Second, if these are really link exchanges, Google may just ignore the links, as reciprocal (and other artificial) links are a game that Google discounts heavily, especially when the sites are not relevant.

Rather than link exchanges, focus on "real" link building with good content, online PR and leveraging your community, partners, etc.