It's not surprising to me at all. People seem to expect a large stake in a company where they are just an employee..and then get frustrated and upset when the owners take a buyout and they get canned.
It's like "working" by going to an apprenticeship. Your salary is lower, but you learn a lot.
If you're going to start your own business in the near future, then it might be worth it to work for a startup even if its a huge pay cut all things considered.
If you are working 80 hrs/week churning out code to realize someone else's "vision" who treats you like a slave not a partner, then what are you learning? Apart from not to get suckered again.
You have no idea if you're going to feel like a slave or a partner until you've already taken the job.
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I'd say try it. Don't assume that you will be dissatisfied based on treatment you can't predict.