Professor Manoj Chaudhury, the Franklin Howes Jr.  Distinguished Professor of Chemical and Biomolecular Engineering was recently interviewed by C&E News about the possible role of silicone in the failure of brake-light switches in Subaru vehicles. 

Automaker Subaru recently recalled several of its models because of the failure of brake-light switches, seemingly, they believe, because the switches  were covered by silicone containing consumer products. Chaudhury has not studied the Subaru switches in details but has observed a similar phenomena in his lab where the conductivity of an electrode immersed in an oil/water mixture is lost due to the formation of an insulating layer on the electrode surface. He believes something similar may be happening with Silicone spreading over the conducting surface of the brake-switch contact points. 
For more details, see the link below:
Manoj Chaudhury

Manoj Chaudhury, Franklin J. Howes Jr. Distinguished Professor, Chemical & Biomolecular Engineering