The ‘non-hyphenated domain’ still invokes a lot of debate in the search marketing world. Most marketers believe that the top results prioritize non-hyphenated domains.
However, non-hyphenated domains rule the SERPs because people prefer to register domains that don’t have hyphens. Also, marketing and branding of non-hyphenated domains are easy.
You’ll see that some quality multi-hyphenated sites also rank well in SERPs. Google has not penalized sites. Sites that are organized properly and have quality content ranks well over the time.
The real trouble is when spammers spam the domain with keywords. Such sites invite penalty.
Given a choice, I would always prefer to go for non-hyphenated sites because they are easy to comprehend.
However, if I have to make a site that’s about finding musictutors, then instead of going for www.findingmusictutors.com, I would always prefer www.finding-musictutors.com.
Also, if you have to make a choice between using a hyphen or an underscore, go for a hyphen. Search engines such as Yahoo and MSN interprets the underscore correctly while Google considers underscore as a character and shows different searches for hyphenated and underscored searches.