Careful what you call this. It isn't backstabbing if you get X shares for your time with the company. You simply need to understand the amount of shares approved, issued and what happens to your shares if additional shares are issued.
Equity in a small private Corporation is basically the sames as in a large public Corp. Either one can issue, or approve additional shares. If you have common equity, your claim will be diluted.
The magnitude of your dilution will likely be higher with a small, growing firm. There are ways around it, just get a lawyer. You can bind in what you're really looking for, you just need to use the law to help you. IANAL