The amount of time wasted these days by employees using chat, Facebook, personal email, Twitter etc. is astonishing as is their attitude when you pull them up on it and tell them to get some bloody work done!
It's also amazing how much it can be the other way though - employers treating employees like machines, thinking everyone should (or even can) be at 100% productivity 100% (and more, by 'expecting' free overtime) of the time, from 100% of employees. Never going to happen.
At the same time, expecting staff to "multitask" which
is a fallacy, by expecting them to respond immediately to multiple interruptions like emails, phone calls and even just people walking up to their desks, and then demanding to know why their day-to-day work has not been completed on time, particularly in an industry where it is seemingly more important to know when something will be finished, than to actually have it finished (read: the number of times someone must stop working on something, so they can produce a report on the progress of the thing they just had to stop working on, and also a report on why the thing they just stopped working on will not be finished on time - with "because I have to keep writing these ****ing reports" as an invalid reason).
A balance between the two is the ideal. Trust your employees, and give them the resources to be productive, and you'll get productivity. Don't trust them, restrict their working practices, and you'll just have monkeys.
Granted you'll get some people who take the urine, but they'll be more than obvious and you should never, ever "punish" the whole because of a few.