I think the relationship with Vagrant has helped Oracle's VirtualBox significantly in popularity. Yes, Vagrant works with other virtualization platforms, but since it so seamlessly integrates with VirtualBox, I think it gets quite a boost. Virtualization is such an efficient and reliable way to implement systems, bare-metal solutions are almost a thing of the past!

• Oracle VM VirtualBox 33.4%

• VMware 22.3%

• KVM 21.1%

• XEN 5.7%

• QEMU 5.3%

• OpenStack 4.9%

• Other 4.2%*

• OpenVZ 1.7%

• Linux-VServer 1.3%

• Symantec Workspace Virtualization .1%

*Under "Other", the most write-ins went to Docker, ProxMox and LXC, in that order.