Group Social Event Scheduling App?

OK, this week's simple idea.

I wonder why there is no app / website to help us coordinate social events?

One that is better than Evite and not requiring everyone to have all their events on some online calendar?

I am imagining an app that:

• allows the event instigator/organizer to poll the potential interested group for idea(s)
• with or without preset dates, but allow people to specify their preferences (strong or weak) beyond busy or available slots e.g. on Thursday afternoon I need to drive my kids to soccer but if it is the only time we can get most of the group to come I will ask my spouse to do it
• with or without preset venues e.g. I prefer noodle bars, but I can do burger joints
• present and rank possibilites by attendance 

I know scheduling is a "hard" computer science problem.  All the better.  If it is easy someone might have done it already.

The user interface may be a challenge too, how should one express fuzzy preferences effectively?

Anyone, just another week's thought.