Just found something on CNN which talks about importance and problems of link exchange from an SEO point of view
Originally Posted by CNN
If you've ever hung up your own shingle on the Web, you've probably gotten an e-mail to this effect at some point: "Dear So-and-so, I believe your site and mine could benefit from exchanging links."
We probably get eight to 10 a week in the CNET News general mailbox, mostly from technology-related companies but occasionally from auto-parts suppliers and watch retailers who either have no idea what we do or few moral qualms about spam.
The idea is that if you can coax a link out of a large site like CNET, Google and other search engines will record that link as a vote of confidence in your site's worthiness and improve your ranking in searches for certain topics, thereby boosting traffic to your site. The technique is quite old, dating back even before Google and its PageRank system emerged as the Web's dominant search engine.