All the Star Trek
series are alrady available on Netflix. I guess it would make sense to launch a series everywhere at once - Netflix, Hulu, iTunes, maybe even try it on CBS as well, to catch the folks who are scared of all that newfangled streaming stuff!
A series only on CBS couldn't survive but packaged with other outlets, maybe.
I'm sure Netflix or Hulu would prefer an exclusive but CBS would have all the clout, since they own the big brand name that will drive viewers to either site.