Seems like your options are: 1. Mutable data (looks nice but can change) 2. Incrementing data (looks nice but can be guessed and measured) 3. Random looking

Seems like your options are: 1. Mutable data (looks nice but can change) 2. Incrementing data (looks nice but can be guessed and measured) 3. Random looking data (immutable and unguessable but ugly) Guids aren't the only option for 3 and some of the others may not look as bad, but it still seems the safest option. Any other compelling reasons to not use guids?