This is actually very close to the following by Tatham Oddie: http://blog.tatham.oddie.com.au/2011/07/14/released-snowmaker-a-unique-id-generator-for-azure-or-any-other-cloud-hosting-environment/

or perhaps even more close to the Twitter Unique ID generator he references: https://github.com/twitter/snowflake

If anyone was going to implement this type of ID generator I'd suggest taking careful note of the comments in the description of the Twitter ID generator that talk about NTP time servers and what can happen if your clocks are wound back automatically. Not a good thing, and actually more likely to occur in a virtual environment where clocks tend to run a little fast!