Sorry to disagree with all you folks who think it's scaremongering and unnecessary but it's a sensible scheme and a legal requirement for employers. It also applies to electrical equipment that employees might bring in to work like radios.
I ran a laboratory at the Univ of Kent with over 100 electrical items in my lab (and some of them were scary). We had our appliances tested at least every year (as was any equipment from photocopiers to bedside lamps) and up to 5% failed due to wear and tear, and even some brand new items failed. On one occassion a visiting maintenance engineer got electrocuted because of faulty equipment and his company, not the university, were prosecuted for not providing a safe working environment.
I also play in a band and some venues insist that electrical items are delivered early in the day so their engineers can test them - it's not uncommon for musicians to get a shock from faulty gear. Third party insurance is required by most venues and is invalidated if just one piece of equipment has an out of date test.
I do agree though that having someone fiddle around and then put a sticker on is pointless - the best way is to plug the gear into an automatic tester which then issues a barcoded sticker which is used to identify both the tester and the gear at the next test (the green ones can be bought and stuck on by anyone without a test being done). The only items that should have a visual inspection are computers and the like, on the other hand equipment that is used in hostile environments like building sites should be tested more often - there are no hard and fast rules but an employer might be required to prove in court that they had taken reasonable steps if an injury or fatality occurred.
If you run a business with even one employee or where you have public on the premises, get your equipment tested but use a qualified person, you might regret it if you don't.
http://www.pat-testing.info/index.htm