Locking of list items
Currently there is no way to exclusive work on a list-item. In document libraries the checkin/checkout feature can be used to prevent mulitple users from update a certain item.
When I'm update listitems in code, I have to make sure, that no-one else is currently updating the item while I change some data.
Potentially someone could update the item while I'm also update the item. Whoever save the item last will receive an error. This could be prevented with some kind of locking of list-items.