as far as I know(from SEO POV) if we buy domain with hypen, actually its like we own 2 keywords in 1 domain, but without hypen, we only own the long tail! for example our domain, Buy-House dot com, by owning this kind of domain, we can easily optimize our website for House Niches, e.g house, cheap house rent house, buy house and etc good news is we can also optimize for BUY related keywords, e.g buy house, buy car, buy gold, buy forex and etc
But if our domain Buyhousedotcom, we can't optimize for plural keywords, such as House, rent house,Cheap house,, buy car, buy gold and etc.( you'll know , no matter what! your adwords score will not reach 10)
does it make different with hypen domain and non hypen domain ? well
if you spam the hell out hypen domain,with Spam tools, it can works very well!
I think the different only for SEO matter, or backlink! i.e Optimization. but not that much for Branding stuff or whatsoever! if you don't believe me you can test, 2 domain, buy-housedotcom with buyhousedot.com, and see which domain that will get decent rangking after link building!(spam jobs) using same tools, and same method!
what if we buy with 3 hypen, house-car-insurance.com,? well that's nice Idea
in fact smart idea. but G bot will take Notice, if your backlink to fast , this kind of domain will easily dissapear!
(maybe not good idea) but personally I don't like domain with Hypen because it looks cheaps
(buy 1 get 2) lol.