First and most important will be the Quick Search Block from the Home Page.Let users add their own fields. There are many who needs it. For example add Country and City Search to be an option for people. There is one mod for that i already seen in most dating website, but Dolphin doesn't have it.
When user is filling the Join Form, after he selected his Country, another
City field will drop down under it, which will let him select his city or region. I know that for this you need a quite large see more geo database with cities around the world and you don't find it for free. But later you can add it as a mod for someone who wants it and to buy it. Or just integrate it into Quick Search, so that the user can add his own cities related to a country. This can be very useful and more appropriate mod for a community script like Dolphin.

2nd and also annoying, is that the user CAN add Articles. So everyone can spam it without any problem.

3rd would be the chat admin. The admin cannot moderate any chat room and has no controle over it, so all you have left is to hope he will leave.