Google posted an interesting Webmaster Help video today about linking. It's basically about whether it's better to link to an original source somewhere at the top of a post, or at the bottom. The answer is essentially that it makes no difference, as far as Google's algorithm is concerned. The link will flow PageRank either way, so as fas as SEO is concerned, it really doesn't matter.
After Cutts answers the question directly, he gets into his personal opinions and discusses what he finds annoying about linking practices.
"I'll just say, for my personal preference, I really appreciate when there's a link somewhere relatively close to the top of the article because I really kind of want to know when someone's talking about it, you know, hey, go ahead and show me where I can read the original source or let me look up more information," says Cutts. "There are a lot of blogs that will give one tiny little link all the way at the bottom of a big long story, and by that time, it just doesn't seem like it's quite as useful, but that's just a personal preference. That's not ranking advice as far as it goes."
"The only other thing I hate - this is once again just personal - is whenever you've got a regular news report, whether it's in a mainstream newspaper - New York Times, AP, whatever - and they say, 'Blah Blah Blah said on a popular webmaster blog that blah blah blah,' and they don't link to the source," he continues. "I mean, come on. Link to your sources, whether you're a journalist, whether you're a blogger, let people go and look at the original information themselves so that they can suss out what they think about whatever it is that you're writing about. So if you just say, 'Oh, it was discovered on a popular forum that blah blah blah,' then we have to go look for it. That's really annoying."
"Again, not ranking advice," he reiterates. "Just asking everybody to be considerate on the web, and share credit, and attribute, so that people can, you know, do the research for themselves if they want to."
As if anybody on the web would ever be inconsiderate.