Why #bitcoin transfers are not instantaneous - by @samuel
▻http://www.rfc1149.net/blog/2013/05/02/why-bitcoin-transfers-are-not-instantaneous
bitcoin is largely similar to cash. The blockchain is built by all the participants (miners create new blocks, others validate them) and acts as a distributed giant counterfeited money detector. As in real life, individuals and business take a risk when they accept cash without putting it through such a detector first. The bitcoin system is similar: you need extra work, or extra time, to ensure that the money you receive is genuine. If you do not want to wait, someone has to take the risk, and this is likely to cost some money