Interesting case study that was able to buck the trend is Atlassian software. I have personally seen bottom up influence in 3 large publicly traded companies land Atlassian very nice (and well deserved I might add) license and support agreements.

They built a product that would usually be sold at the VITO level, gave it away for open source projects so it became defacto to developers and viola Jira is now replacing IBM products in many enterprise software development shops as we speak.