Tim Bray brings up an interesting problem: given an "official" link (with bad urls, and the propensity of government sites to change quickly), or something like Wikipedia - which do you choose? It's a deeper question that you might think:

I’d be astonished if the Wikipedia suddenly went away. But I wouldn’t be very surprised if it went off the rails somehow: Commercial rapacity, legal issues, or (especially) bad community dynamics, we’ve seen that happen to a whole bunch of once-wonderful Internet resources. If and when it did, all those Wikipedia links I’ve used (396 so far, starting in June 2004) become part of a big problem.

[Let me be clear: I am an unabashed partisan of Wikipedia. I think it is a triumph, a piece of evidence that being human is no bad thing; and I’ll do what I can, when I can, to help it. If I think I see it going sideways I’ll be in there shrieking and fighting.]

We make that choice anytime we link, actually - if we link to a blog, it could disappear and be replaced by a spam farm 3 years from now. It's the downside of making "permanent" posts in a transient medium.