Receptional_Andy - 8:12 pm on Sep 24, 2008 (gmt 0)

The answer depends a little on what effect you're aiming for. You're unlikely to see much tangible SEO benefit from linking to the same word multiple times from a single page - once will perhaps do the trick.

There's also the editorial side, which might make multiple links to the same page burdensome - you could easily end up with more links than actual text on a page, which (if nothing else) would seriously harm legibility.

From a copywriting point of view, you might want to link every occurrence of words relevant to important pages, since readers are likely to both scan the content, and jump to particular sections, and so they never see the other links.

Most sites don't link every occurrence of a word or phrase to a particular page, so I'd say that's the de facto standard. That doesn't mean it couldn't work for your site, though.