Here's one of the reasons I prefer putting my retirement savings into an ISA instead of a Pension: you never quite know what the government is going to do with the money in your pension...
Already in my lifetime, the rules have been changed on pensions meaning that I can no longer access "my" money until I'm 55. It used to be 50 and I suspect it will be higher still by the time I finally retire.
UPDATE 30th Sept 2013:
Another excellent article from Merryn @ MoneyWeek: