I see vetos as a step along the journey to opening up an existing relationship. It's one of those safety line things that many people have in place when testing out the waters. All I can say is be open with anyone who you are considering dating about there being a veto power in place so that individual can make the desision whether or not they want to get involved with you. You might find as things go on that there is less and less need for veto.
I used to be a strong defender of veto power but I'm not a big fan of it anymore. I figure the only person you can really make desisions for is yourself. If a situation isn't working for you it's best to talk it out and find a mutually agreed upon solution. Plus the person who is having the veto used against them is a person with real emotions too and it's got to be hard being in a realtionship where you have the possibility of having it ended by an outside source over your head all the time. I wouldn't chose to be in a relationship like that.
Everything will be ok in the end. If it's not ok it's not the end.