Yes, but you can link your account from each studio to the same UV account, so you can access them all in one place (UV.com or Flixster depending on which interface you prefer).
I know, however it is still unbelievably stupid.
With iTunes digital copies, all I need is an iTunes account, no matter the studio.
But with UltraViolet, I now not only have an UltraViolet account but also a Flixster account and a Sony Pictures account...And that's only after two films from two studios.
Why can't it simply require *one* account, with UltraViolet?