US companies operating abroad could find that patents filed in the US don't protect their intellectual property in the rest of the world. 

This week, the Supreme Court in Washington decided in favour of Microsoft against AT&T, which had alleged patent infringements in overseas Windows sales.
This decision is expected to reduce the damages awarded in patent cases because overseas sales wouldn't be included.
In another, unrelated, decision the Supreme Court made it easier to challenge patents if they cover products that are obvious combinations of existing technologies, citing a law that an invention my be new, useful and not obvious to merit a patent.
Both IT and bio-technology companies are concerned that it may be more difficult to attract investors if there's a chance patents may be invalidated at the end of lengthy and expensive development efforts.
Patents are big business and many technology companies derive substantial revenues from licensing their technology. For example, IBM collects about $900-million a year from licensing its intellectual property.