First off, the SEO value of a domain is only one (very small) factor in search engine algorithms.
I focus more on SEO than domaining and I would highly disagree with this statement. Google's algorithm puts a great deal of weight on keywords in the domain, especially exact keyword match domains. Yahoo and Bing give even more weight in my experience. From all the testing I've done, even the extension matters noticeably. I have had exact match .info names with no other extensions developed have trouble ranking in Google, while my exact match .com names with more competition for the keyword rank much more easily. I'm not sure why this is, but my theory is that the algorithm basically says- if you've captured the flag (exact keyword match .com domain) and have your other on-page SEO ducks in a row, you must be pretty authoritative for that keyword and you start with an advantage.
Think about it - if you have the exact match .com in a competitive niche, you were either in that niche early or invested a good amount of money into acquiring the domain. I don't see how any good SE algorithm wouldn't put a good amount of weight on this factor based on the seriousness about the keyword/ niche it displays.
I'm not saying it's the biggest part of the algo, but it's definitely very important and gives you an advantage.
Back to the original question - no dashes. Search engines are great at picking words out of a URL and Google is getting really good at matching words up with synonyms in context to find other relevant results. Dashes should be looked at like .info domains or any other domain that is likely to be available for a lot of good keyword phrases... spammers tend to use them a lot, so they likely pull less weight in helping you rank. Also, if you want return visitors, dashes will kill you.
Nothing against .info or dashes though. I own plenty of both, but I would trade them in any day for the no dash .com versions.