Things change very fast in startups. As your problem space emerges, you will be changing technology also to fit that picture. Strict specialists are rarely good in that kind of environment.

If you're doing a standard web app stuff that doesn't push any boundaries of science, you probably won't need a specialist until after you've hired four or five engineers anyways.

I didn't say strict specialists, I said someone who had something they were strong at but still able to adapt.

I'm a CTO hiring this sort of person right now.