If I have a site registered and running on ThisIssomething.com for example, does registering This-Is-Something.com and redirecting it actually help SEO?  Or is it mainly to protect your brand?
Does registering a second domain name with the dashes help SEO?
seo;domains
It's mainly to protect your brand. The dashes don't help search engines determine keywords unless the words are ambiguous like expertsexchange.com or whorepresents.com. In those cases it may help although anchor text in hyperlinks (internal or external) most likely removes the ambiguity.See this related question for more information on why it doesn't help.