Are your referring to your site being banned? If so, the consequences can be horrific if you were relying on search engine traffic. Some visitors also like to research a domain before doing business with them. If your domain is banned, it will no longer appear for a domain name search, this might also deter someone from furthering a business relationship. The list is really endless.
As far as what what you can do about being banned (if that is what you meant by "chucked out"), that really depends on why you were banned to begin with. Was it because of linking to a bad neighborhood? Were you cloaking, using hidden text, doorway pages or any other on page or off page spammy techniques? Has your ip address been banned for spamming?
Whatever the reason, you first need to identify it, clean it up and send an apology e-mail to the search engine in question explaining how you are sorry and ask if you could be included again. But, there are no guarantees that the ban will be lifted.