How much did the original founders spend both in time and in money before you came along.
* How much have /you/ spent in relation to that?
* How affected was the outcome of the business by your presence, did you accelerate the growth, did you take it the extra step, can they survive without you etc.>>
I've done this math, valuing time at the market rate. I come out as about a 10% contributor, but they obviously can't give me 10%, since there need to be points for the option pool.
I was offered 2%, which seemed really low, but I was told that this was because the CEO wanted to conserve points for future hiring. I was also told the low number was because I wasn't relevant to getting the first round of funding (which appeared to be imminent). However, funding came later, at a time when I am relevant, and with 7 months on the line, I don't think this is enough, unless a large number of programmers much better than I am are hired (and they mentor me).