This is what the FAQ has to say about status update limits:
Updates: 1,000 per day. The daily update limit is further broken down
into smaller limits for semi-hourly intervals. Retweets are counted as
I'm a little unclear as to what exactly is meant by "further broken
down into smaller limits for semi-hourly intervals". Is the 1000 per
day limit divided evenly between the 48 half hours each day (around 20
or so tweets per half an hour?).
Also, I'm assuming this limit applies to each unique account?
Is this limit absolutely fixed? Or is there some equivalent to
"whitelisting" for status/update limits as well?