In his defense, he was fresh out of college and thought it wasn't that big of a deal. So I sat down with him and explained that it WAS a big deal for a company our size, and he was super apologetic.
In summary: Don't screw people over unless you work in an anonymous, transactional industry, which startups aren't.
When I took a position with a small company way back when, I told them up front that I had a summer job working for my dad for 3 weeks each year. They were very accommodating.
This does not address the lack of time off for a vacation, but that is another post...
I've found through both first- and (close) second-hand experience that this generalization doesn't hold.
The OP's poing about assessing openness and honesty of the management is well taken.