With the most recent version of MSDE I believe you can have an "unlimited" number of connections to it, but after 5 connections performance throttling occurs. In other words, I think the software deliberately degrades response times once more than 5 connections are made and 10 is really the limit. I also think that you are also restricted to a maximum of 2GB for each database. Hopefully someone will correct me if I'm wrong, because I have an app that uses MSDE for fewer than 5 users and SQL if the location has more than 5 users.