The mention @ user in particular can be very useful - if there's a particular user who is knowledgeable with a certain problem and may be able to help, it's a good way of attracting their attention to a thread. I don't see the need to mention more than 2 or 3 users in a single post.
Eg: @
Citroënbender and @
russellw know quite a bit about this, they may be able to help.