A little while back I was chatting to someone about SEO and the power of outgoing links. In the bad old days your client would ask you to build a web site that had no links leaving the site or put some horrible confirmation page asking you that you are leaving!
Whats interesting here is that by not having any external links you are reducing your interconnections with other sites, and so reducing your ranking in search engines. Not only do most search engines allow you to search for linked pages but each additional connection in either direction will increase the weighting that matching symbols (words) in those documents have the same implied semantics. This is just like a neural network where each additional connection re-enforces the bond further increasing the chance of a pattern match.
Add to the fact that incoming links, trackbacks and pingbacks are very common on blogs and other modern publishing tools and those implicit back links become explicit.
So if you want people to link to you, you should link to them.