I was reading from Corey Rudl Internet marketing series and he stated "that if you own a website you must link to relevant sites that are in common with your theme" Do you think this is true and why do so many sites have different categories on their webpages where you can put your link in specific category?
Relevant link exchanges or one-way links from relevant sites is becoming more and more necessary to gain good rankings in Google. The other search engines (Y! and MSN) doesn't matter too much.
Somehow relevant linking is a big factor in serps, sites that has misleading categories due to inbound links from my point of view get penalized...so better gather relevant links to attain good ranking.
Your right. Not all of the links HAS to be relevant but the more you have the better. What it does it tells G what your site is about so they can classify it and they can tell what kind of neighborhood you run in. I think the occasional outbound link to a relevant site is important. You maybe sharing some PR but you are also again telling G who you are and where you run. Thats IMO. Others differ on that and say no outbound links is better. I guess you need to see what if does to your site and adjust accordingly.
Linking to useful and related sites is good for your visitors and search engines would be foolish to ignore it. Google are always saying you should create sites for users rather than search engines and I reckon the algorithm will be designed with this in mind.