I love the way Twitter has taken off. When it started I thought it would be a fad but I've been proved very wrong! Presuming you are trying to launch a fairly new business, how many Tweets a day is ...
the question is not the quantity but the quality.
search for tweets about your product/service and send them quality content to solve the problem anything else is just spamming and a waste of time
Twitter maketing secrets on DVD
People will ignore you if you start promoting your business from the get-go. You have to add value. Share articles you've read and join conversations. One guy I study suggests that for every 10 Tweets one could be promotional.