According to market analysts Samsung is now the biggest Apple competitor on the tablet and phone market. The reason of these legal suits is that Samsung design closely resembles the one of the iPad. Apple has a lot of its design elements patented and seeks shoot two birds with one stone and keep Samsung away from selling tablets and then maybe even phones.
After Apple’s initial complain a court decided that it can not deny Samsung the right to compete. Apple of-course appealed this decision and now after it was decided that Samsung Galaxy Tab 10.1 is banned in US Samsung still has to undergo a trial based on the patent dispute case.