Well, uddeIM is not a forum, it is a PMS component, so people should be able to send messages to their friends. And when they send messages to 100 different people (e.g. organizing a party) this is ok (in a forum posting 100 messages would be spam indeed). In uddeIM 1.1 posting a larger group of people would be easier using contact lists in future.
Nevertheless I see the problem with communities where people register just to post spam. In uddeIM 1.1 you can enable Captcha spam protection for (un)registered users.
When you have a closed user group, spam is not a problem at all and you will enable contact lists and do not need flood prevention, in communities like Joomlapolis this feature might be useful for a very small group only (maybe special users or admins only) and I would not recommend to use it for all registered users, even when we have several anti spam and flood prevention systems implemented.
I have already an entry on the tracker, maybe it will be an option to let an user post only one message in a certain period of time, I have to think about it.
uddeIM & uddePF Development
CB Language Workgroup
CB 3rd Party Developer