Visa, MasterCard and American Express all support contactless payments that only require you to tap your card close to the terminal, and usually PINs are then not required for low value transactions.
The value that doesn’t require the cardholder to input PIN number is usually set to a relatively low amount ($20 – $30) but love the fact that in Australia no PIN is required for transactions up to AU$100!
Although there is no PIN required, I believe that merchant terminals in Australia are doing regular authorization because printing out the receipt is not instantaneous. Usually, when the limit is low the transaction is instantaneously approved.
There is a Wikipedia page that lists various amounts that different countries have for transactions not requiring PIN number (access here).
I wish that other countries where merchants can decide the amount requiring one to input the PIN number would be set to a reasonable amount such as in Australia.
And I love the fact that in London you can use your contactless card to pay for transportation and it automatically charges you the correct rate where daily/weekly maximum amounts are involved (just remember to use the same card).
Not sure if it is the issuing bank or the merchant that carries the unauthorized transaction risk when contactless cards are used.