There are a few perspectives on this. The first one, which everyone else has voiced, is that verbal promises are worth nothing. Things can always change and you could be left behind...
However, in some ventures I have been involved in, equity distributions are not decided in the very beginning because you don't know enough yet. If you give equity too early, you can mess up big time in many ways. In my opinion, the best thing you can do is sit down and talk through the terms. Figure out what is going to impact the decision about how much equity you do receive, and at what point in time that is expected to happen. Lay out some terms in advance, even if the actual equity percentage is not laid out from the get-go.
The last thing to say is that contracts are only as good as the people who sign them. Trust should be the #1 factor in your decision to deal with business partners. That said, you have to protect yourself, so do what you are comfortable with and roll with the punches. If you are not getting paid and don't have a 100% promise of stock in the company, the time you are putting in right now is "volunteer" time, and that is something that only you can decide if it is worth to you. I wouldn't let the lack of set deal terms scare you off just yet, if you think this is something you could really benefit from. But of course, it's all your call!
We have bootstrapped Club E Network, a broadband TV & Social Network for entrepreneurs, from the ground up. We started with nothing, took on great partners (including a technology partner to create the BETA version of the social network), and have brought it in a few months since launch to the range of tens of thousands of unique visitors a month to get us off the ground. Now that we are at that level, we will be taking some investment to further develop the next generation of the site (much more advanced) as well as continue developing our original television series.
I think not having money gives entrepreneurs a real advantage in some ways, because you are forced to REALLY think hard and discover innovative ways to market and improve your site, without cash. It's been a very interesting experience, and I definitely believe something that is beneficial for entrepreneurs to go through, as opposed to taking money right from the start.