From livemint.com, because dead mints tell no tales:

With the reforms, the US patent office sought to limit the number of times to two that a patent applicant can file "continuations" of patents. Currently, there is no limit on the number of times that a patent holder can keep updating its patent claims through such filings. The draft law is now under consideration of the US Senate.

The patent reforms in the US are aimed at eliminating frivolous patents as also invalidating several existing patents that have received such protection through "continuation" filings based on simple modifications. This would help generic players to enter the market with more products as the legal expenses will go down.

With the provision of post-grant opposition, generics companies will get a new opportunity to argue against the unsubstantiated claims made by the patent holder without going to court of law or infringing the patent - both expensive options.