Why do bitcoin prices vary at different exchanges

Below is a link to a great article about how and why bitcoin prices vary between exchanges.

If you are able to setup multiple accounts with multiple exchanges and act quickly there are opportunities to be had by taking advantage of the the price differentials.

thttp://www.freebitcoingiveaway.co.uk/why-do-different-bitcoin-exchanges-have-differing-prices/

You can see the price differentials here at the popular blockchain website. These are often as wide as 10% of the total value.