IP bans will be reconsidered on a case-by-case basis if you were running a bot and did not understand the consequences, but typically not for spamming, hacking, or other abuse. If you are responsible for one of the above issues.
Running a web bot/spider that downloaded a very large number of pages - more than could possibly justified as 'personal use'.
Your current IP address has been blocked due to bad behavior, which generally means one of the following:
