If you have been banned from a search engine, and you have been in business for quite some time, there are many things you can do in the damage control dept. The most important thing to do, is act quickly.
I will assume, that any site posting their problem in here, was banned in error, or banned, buried in the rankings, because they crossed the line in error, not deliberately. If you have been in business a long time, and an engine has penalized you, it can be devasting to your revenue. If you are new, recently acquired top ranking, the solution will be different, because you are not losing major renenue, and can better afford to try to appease the search engine God with a more time consuming process. But, for an established site with heavy traffic, and major revenue, this is what I do, and it works very well.
Register, if you didn't already, the most common variant of your domain name. In many cases, this would be the hyphenated version. Next, go through and clone the entire site to form the second site. Now, go back, and change the meta tags on the pages you submitted to search...this will not work with google: change all meta tags, and move the content around a bit on the pages....enough to make it unique from the old pages. Publish it, and add it to search.
Frequently, I have clients, who in the course of building their pages, make a minor goof by accident, but it's enough that all the top 3 rankings I got them are gone in one engine overnight. Often, just changing one page will work...sometimes more is required. By doing this, we create a new site, it gets ranked, and the old site will still have the rankings in the other engines. From this point, you work to slowly define each site as unique, and build them independantly. You will get double exposure, and because each site has some content unique from the other, you can justify the two listings.Add some special depts to one, that the other doesn't have.If having two sites concerns you,after the second site is back where the first site was in ranking, remove the first site.
This is done after, creating a new page of the one banned, with slight modifications, entering it into search, and it still wouldn't rank. It is a last resort solution, when all else has failed. I can create a second site of over 100 pages in under an hour for my clients who built their sites using the same software I use, and can have the new site fully launched in 48hrs ...but depending on how you build your pages...software, html... you may be in for a long haul, and cleaning things up and pleading your case to the search engine God, may be an easier road to travel.This is where chosing the way you design pages, is extremely important.. because you never know what bandaids you will need down the road to repair a disaster, when the search engine God has slapped you in the head..
If you were dropped from ranking because a competitor cloned you... that is legal brief time.
It's worth a penny...drop one on the ground for someone to find.