Brad Burnham, from Union Square Ventues, describes the problems faced by small companies whose independent inventions overlap with established patents:

Our companies are being attacked by companies that were not even in the same market, very often by companies they did not even know existed.

And proposes a solution:

If, on the other hand, the troll was required to show the startup had some prior knowledge of their technology, the burden would be shifted to the attacker, and this blatant abuse would come to a grinding halt. If you believe as I do that innovation is key to social progress, please support patent reform.