You can, but your levels of support from MS will vary. Make sure you understand your versions and their supported MS backup methods. For example, snapshotting a DC with Windows 2008/2003 is unsupported as detailed in MS875495.
Personally, I don't backup VMs that are DCs, use agented backups for Exchange and backup AD cert VMs as VMs. I don't like to use unsupported methods, but whatever approach you use test it thoroughly.
Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com
