Hi,
Welcome to the communities 
Hypervisor reclaim wrong memory and cause the virtual machine crash? It will never happen
.A balloon driver is loaded into the guest operating system as a pseudo-device driver.It has no external interfaces to the guest operating system and communicates with the hypervisor through a private channel.If you want to read some good post ,please do check >http://blogs.vmware.com/vsphere/2012/02/disable-ballooning.html