The essence of a good trading strategy that leveraged Tweets would be to perform extensive back-testing on which sources were remotely influential and/or reliabe. trading decisions would never be made based on an unproven source. At the very least, a trader would get a jump on knowing when something major was going on at a macroeconomic level that would indicate stopping/switching off their trading model. Reliable Tweeters would become more prevalent as the potential to build brand and reputation for value gain - e.g. promoting themselves or their company, potentially a research firm, is extremely motivating.
this is such a bad idea -- people will set up bots spewing fake information and boiler-room 'stock tips' of the sort already passed around in junk emails
