Topic: data store thoughts

I have been thinking about what is the best solution to solve the problem I am currently working on.

I have a site with 2 different users, priviledged users and visitors. I want priviledged users to have the ability to create a list and add events to it. Visitors can subscribe to that priviledged user and vote on the events and well as request new events. The priviledged user will only create this list for one day and the most and then it is deleted.

I have had problems thinking about the best way to accomplish this. Obviously memcached or some equivalent will be used, but as far as back end store goes will this be faster in mysql or a nosql data store such as mongodb?