In order to have an affect one must be of concern to the company.
When the drunken whore randy roads (I don't give a shit how her name is spelled) made that hilarious little skit about assassinating GW Bush, HP/Agilent was running ads on errAmerica. At the time we were buying about $400,000 of their high end analyzers and meters a year. I made a call to the local distributor and said that if HP was going to support errAmerica then I would be looking to sub all their equipment. I got a call from the VP of sales western division that afternoon assuring me that HP had pulled all of their ads and that there was no need to go to our second sources. From the conversation, I learned that I was not the only one making their displeasure known to HP.
If I had been a DUchebag that didn't buy from HP, my threat would not have gone a millimeter at HP.