Sometimes, Macros are used to store sensitive information like passwords or shared keys. (think VMWare, Telnet, SNMP).
When viewing the macros that are configured on a host these are put on screen without any masking. This would allow someone looking over your shoulder to easily spot these secrets. This is even more of a risk in 3.0 where we will be seeing all inherited macros as well.
To prevent this scenario, I would like to be able to specify if a macro should be masked in the frontend, perhaps via a checkbox. To see the macro value one should click on a 'unveil' button or icon.