Teammates have pushed me out of our venture. What to do now?

I'll take a contrarian approach. If 3 out of 4 founders say they don't value your future contributions, you should take a hard look in the mirror and ask why.

What parts exactly did you contribute? Are you a developer? I'd guess not. Designer? Marketing? If you were great at brainstorming the initial idea, but that's all you did in 5 weeks, then that's a classic deadlock: you are attached to the idea, but the rest of the team wants to kick you out.

That being said, you probably should be able to negotiate something (equity) in exchange for letting them run with the baby. An advisor who gives a few ideas 3 times a year gets 0.5%. The most I would consider, without more details, would be 5%.

First question, before what to ask for, is how much can you prove you did? Do you have have a body of proof of your contribution? If you didn't have any agreements leading up to the creation of "whateveritis," can you show your contribution to it. Wireframes, design docs, ppt, code, anything?

You need to provide more information on what your role was, what you contributed and what you verbally agreed to in the beginning. Then an attorney can provide you some sound advice.

For example, copyright law provides protection when the expression of an idea is fixed in a medium. This means that if you wrote software that was not a work product, you own it. They would need a license. Same is true for any other expression of an idea that became part of the venture.

Again, it's too much gray area to answer with the information that you have provided.

Agree completely with Sharon Drew. The original poster really needs to quantify their contribution to the effort.

What I fear is that this was a "skunk works" project and everyone pitched in without much regard for formalities, communication or written timelines - that's what an incubator is all about, after all.

In a normal project you'd have an email trail that could be used to reconstruct the roles that everyone played. This is probably not the case here unless the project management tools that were in use support this.

The O.P. needs to document their contribution. If they can't describe it, then eyewitnesses may need to be called in to document that the O.P. played a continuous role in the project inception.

Just guessing but a value for the project as it now stands would probably have to be calculated. This would be based either upon prorated contribution, or upon a fraction of the entire pie (IE, five members, each member's stake is worth 20%.)

And then the O.P. should be bought out based upon their share of this value.

That's just one model. Another model might be to pay the O.P. a fair market labor rate for the time they spent working in the project.

In any event... get an attorney.

The team mates sound incredibly stupid to have done this "ambush", considering that they want to take this project to the next level.

At this stage the company consists of "branding, soft prototype, wireframes and meetings" ... How much is that worth?

The answer is Not much: It's essentially a well fleshed-out idea, and ideas aren't worth much more than the paper they're written on (try to sell an idea w/o execution to a VC).

How much would someone buy the company for, right now? How much of that worth did you contribute? If, as assumed above you are the graphic designer, then you'll be entitled to much less than someone that contributed a novel algorithm...

Of course, the converse of that is that you should feel free to go forward with the idea on your own, too... And divide 100% of the equity as you see fit.

Looks like you didnt enter into any initial agreement or arrangement designating yourself as an equal owner/ partner in your start-up. Without any legal documentation, it will be very difficult to prove your participation in the e-commerce venture. Is the potential investor aware of your contribution in the development process?