How many Twitter Accounts do you need

I was asked today, how many Twitter accounts are needed. Do we use one for personal and one for school, or do we have one account and use it for both?
Unfortunately, this isn't a simple one to answer. There are a few impacting issues and one needs to be clear on the goal and purpose of the account before this can be answered.

How Twitter is changing education

Phil sent this out on the the email stream. A good read:
Link: How Twitter is changing Professional Development and also Why Educators should join Twitter

How to set up a Twitter account