If I recall correctly, CNN had a segment on it a while back here in the US.
Here almost all the 0% offers are for a few months. When card holders transfer money from an interest bearing card to one of those 0% offers it gets transfered as a cash advance which is calculated at a much higher % rate than a purchase.
I would imagine transfering the credit limit to some sort of banking product is considered a cash advance also.
USA savings accounts don’t pay much in the way of interest so the money is usually put in a higher yielding choice such as a a money market account, mutual fund or CD which may carry penalties for early withdrawal should you need the money for something.
Plus you still have to make the monthly creditcard payments, miss a payment on the 0% card and things could fall apart pretty quickly.
Imho, it is not worth the risk. The downside is too great.