buckworks - 9:06 pm on Dec 10, 2009 (gmt 0)

The main reason to place a link on a relevant site is to attract an interested visitor.

If you consistently aim at that, the overall signals of relevance that develop within your link profile will reinforce your own theme with pretty good clarity.

Not every link needs to be perfectly, obviously relevant, as long as your overall link profile is sending enough signals that help the spiders decide what your page is about.