Bitcoin is the most talked about and top class security for transactions in the world today, where no third party has a hand and there is no chance of losing money. Bitcoin is accepted by more than thirty thousand organizations around the world like WordPress, Microsoft, Wikipedia, Overstock. Its popularity is constantly increasing day by day.
my own think
In this thread, people mainly focused on the part about losing money, so I think there is not anything to add to that, but I'd like to focus on the part I marked in bold. Bitcoin can be used without intermediaries, but that's not how people usually use it. Exchanges 'have a hand', services like Bitpay, some wallet providers as well. And as for its popularity increasing, while the number of new wallets keeps going up, the rate is so slow that for now Bitcoin doesn't stand a chance to catch up with major online payment providers as in about 20 years it will get where they are right now (I've counted this once by using a number of Bitcoin wallets, the rate by which the number is currently growing and the number of users of services like Apple Pay).