You've had lots of answers but I have a few other points that are worthy to mention... The #1 key / function on a Bloomberg terminal is the Message key. Just l

You've had lots of answers but I have a few other points that are worthy to mention... The #1 key / function on a Bloomberg terminal is the Message key. Just like people are on Facebook because other people are on FB and not MySpace is the driver behind BB's message function. Bloomberg messages are key for relationship maintenance and informal (or even semi-formal) information exchange. BB is a little hard to learn how to use because of all the special keys and function short codes. But because of those special keys and functions, once you are trained, the system is blazing fast to operate. Blazing fast in a trading environment is especially important to grumpy trading staff. Which gets us to deal capture... so with the BB messaging system being so popular and in the early days being used to talk about deals, Bloomberg created a deal capture element to the system. So in addition to chatting with your street counterpart, you could formally confirm the deal you just messaged with your buddy. So take the social, add the deal capture, and add the fast & reliable, you have a damn good vanilla dealing system with zero overhead beyond monthly terminal cost, which you are paying anyway. Unlike Reuters market data client-side infrastructure, BB terminal implementation requires low technical knowledge. Leased line and a black box communications server and bango you are up and running. Reuters, you need multiple Unix servers, so you need a Unix admin plus 1 more guy in case Unix admin #1 goes on holiday, plus leased lines, plus the comms equipment, plus this and plus that. My old firm had 1 employee dedicated to untangling Reuters bills as there were user costs, systems as data user costs, depreciation costs, real time data costs, blah blah blah. Reuters billing had elements of self-auditing and internal real time data subscription management. BB bills are a list of BB terminal IDs which are easily mapped to user X and department Y. BB real time data feed costs are tied to specific user. You could process a Bloomberg invoice in 30 minutes with a temp staff.