I don't think undoing a vote would be a valuable feature. One of the nice things about this site is that it is minimalistic.
Undoing a vote, even if it is useful, would add clutter to the UI. Because I always enjoy the sparseness, but would rarely want to undo a vote, I think the site is better off without the feature.
The images are a bit fuzzy looking. Also, the tagline is a bit of a mouthful. How about: "All of your friend's updates all in one place" instead of "Readr delivers your friends' latest updates from around the Web.
Based on this info you need to cut ties with these people. Equity is for risk takers. If you are taking all of the risks, then you should get all of the equity.
Now, if you have already shared the equity, then you are in a big bind.