I think that the real power in twitter for Joomla devs is not necessarily in its marketing potential, although thats certainly an important part of its use, rather it is to help cultivate a sense of community, put faces to names and personality to profiles. You don't need to follow the people below but Im sure you will enjoy their tweets if you do.
@brianteeman - Often contentious Joomla tweeter with a good sense of humour.
@connectr - One of the highly skilled guys behind Joomla Junkie/Prothemer
@joomlapraise - Developer and awesome designer from Joomla Praise
@coryWebb - All star joomla developer and howtojoomla guru
@laFrance - Joomla powerbroker and always interested in a short 140 character conversation.
@amystephen - often contentious Joomla tweeter with unmistakeable passion
@joomlaworks - k2 developer and joomlaworks.gr supremo
@zuno - Huge fan of his Joomla design work
@alledia - Joomla SEO guru and Joomla trainer
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