Yeah, well a lot of SEO people are just parrots who repeat what they've heard.
Does "Amazon" equate to a massive multi-product marketplace somehow? How about "ebay"? "Flickr" is so much like "photo hosting" that you can see why they're such a popular search result. And so on.
Having key search terms in your domain name lends a tiny bit of weight to the overall result ranking. The link text, page title and H1 tags will do more for you though. So will text in the url itself (www.foo.com/these-are-my-keywords).
All valid points on the SEO stuff. One thing to keep in mind is that the age of the url is important too.
One thing I would point out is that everything else being equal a good domain name will generally get more clicks. The higher CTR will eventually lead to higher results in both the natural and paid results. A good domain name is also important for branding and other forms of advertising.
I am not going to remember an IP address unless my dork quota hasn't been met that week.
Those domains are still quite valuable.