BT Sues Google for Patent Infringements (Wired)

Patents are filed for many reasons. One of which is that some people consider it of value, i.e. you can use them as marketing towards both consumers and investors. Also, against similar-sized competitors they can be used both offensively and as deterrents.

A switch to trade-secret law would be very much preferable for software-patents, especially for user-interface-patents. These are by nature public, the patent-disclosure has zero value over a trade-secret. (having how to implement one-click shopping be a trade-secret, doesn't at all make it harder to re-implement it)