I agree with piatkow however some may say that without the "-" is best but from a legability point with "-" can be highly advantageous however do ensure you own both, don't try and compete against someone with an already well-established site in the same widget indsutry with a "-" versus without.
I am noticing more and more these days especially in UK TV advertising "-" is being used a lot more.
What if you have the example-one-two.com and the exampleonetwo.com is taken but is parked with adsense? The example one tow is not a tradebrand name, it's a niche market. If the example-one-two.com gets going and becomes well established, would it be ok then?
Just a small consideration: you'd be amazed at how many people search for terms without using spaces like "onlinewidgets" etc. Although Google does some intelligent seperation when it recognises words, if the words are not commonly searched phrases (ie "pigeonwidget" or "buyamericanwidgets") then I find the non-hyphenated generally provides a better match.