In a quick Google search, I found this post referencing support by the Business Software Alliance, which includes Microsoft, Apple, and many others: http://thenextweb.com/insider/2011/11/17/which-tech-companie...
Its initial support did lead to a couple of firms quitting the BSA though, notably Kaspersky.
http://arstechnica.com/tech-policy/news/2011/11/even-the-bus...
There's that expression, "Don't hate the player, hate the game". In the same way that I'm not a fan of a basketball player flopping to draw a foul, I'm not a fan of a company supporting this bill. I totally understand why they do it, but it's not in the spirit of the game IMO.
The bigger problem is the way the game itself is set up. Most people think it's a good idea to hand over their power to a small group of people who get to make decisions for everyone. Businesses see this and figure out that they can realize the benefits of the larger group while only incurring the costs of catering to the smaller group.