I would disagree with Urb on both counts..
The domain name you use is only part of the picture as usual.. and a well structured page on a non-hyphened domain could easily outscore a hyphened domain.
IMO - You wont find a "-" in a search as it is an operator and you will find "_" as it is a character.
http://www.google.com/search?num=50&...dancers+-brain
http://www.google.com/search?num=50&...+dancers+brain
Also as the domain name is only part of the whole picture... you can out rank "keyword" domains, with a domain that does not even contain the keyword.
I am ranked top #10 at Google for "keyword1 keyword2", with a domain that does not contatin either keyword...while
keyword1-keyword2.com
keyword1-keyword2.net
keyword1-keyword2.org
don't even get in the top 100.
Thats said... using a domain with the keyword you are tragetting can help, but as usual it is not THE answer.
Re: question #2 - NO!
Look at
http://www.google.com/contact/spamreport.html - the number one check box response is for "Hidden text or links"
....
DD