I'm sure you've seen those URLs -- www.domain.com/4-star-hotel-in-barcelona-spain.php. The question is: is this a tactic that we consider spammy?
Not really, according to a High Rankings Forum thread. On the other hand, if it was www.domain.com/4-star-hotel-apartment-penthouse-keyword4-keyword5-keyword6-in-barcelona.php, that may raise some eyebrows. Additionally, if you think about it, unless you change the post slug of a WordPress post, thousands of these long URLs are generated every single day. (Tip: Shorter URLs are easier to remember and rock.)
At Cre8asite Forums, the question regarding dashes in a URL is discussed. Is it better than an underscore? Back on the High Rankings discussion, dashes are the default delimiter, if that gives any indication to a widespread preference, but it really doesn't matter.
But if it comes to the actual domain name, it's a lot easier (for you) to go with one that lacks the dash to make it easier for users to remember. They're less inclined to type the dash and it takes a bit of a learning curve. I found that adjustment necessary with brand new webmaster forum Webmaster Talk.