How much information should I divulge about on-going unpublished research at a conference? I'm developing a paper right now based upon some of my preliminary results, and I'm attending several conferences to present and get some feedback on my results from other experts in my field.  A thought occurred to me that because my work is yet to be published, I there is a potential for others to steal my idea and publish before I get a chance.

I'm probably over-thinking this, and there is little chance of it actually happening.  But I'm curious how frequently this happens in scientific domains.  Do people go to conferences to steal ideas?  If it does happen, how can I best prevent it from happening?  Obviously, I want to share my ideas with the world, but I don't want to lose a chance to take an idea into fruition.  What should/shouldn't I share about my research before it is published?  Should I simply wait until my paper is accepted before I go on the conference circuit?

Update:
My field is computational science (not to be confused with computer science).
This will really, really depend on the field you're coming from - or even the sub-field. Take two examples:


Mathematical epidemiology: If I present a paper with a nice infectious disease model, with the equations, the parameter values, and some numerical results, but I haven't tackled anything analytical yet, you could very well - if you could get all that down - beat me to publication.
Observational epidemiology: I could tell you everything about my study but, without access to the raw data, you'd have to go find your own multi-year hospital acquired infection cohort to study. Good luck with that. And if you still beat me to the punch? Well, I probably deserve that.


Generally speaking, for in-progress stuff, I present enough for people to know what I'm doing, comment on it, etc., but not enough to fully replicate the experiment without coming to me for more information. For example, some folks I'm working with struggled with whether or not to present a theoretical result without its implementation done yet, because someone could scoop us with the implementation. We decided for the audience I was presenting to, that was...unlikely. For another audience? They'd get the theory in broad strokes, but without enough information that the theory alone is enough of a springboard to run with the paper.