Billable vs. Unbillable Default

We recently received a feature request to create a preference to make time in Intervals unbillable by default instead of billable. That way, when applying time to a task or time in general the "billable" checkbox would not be checked. If you are using Intervals for unbillable time you could always enter everything as billable...it won't hurt anything. A few customers currently do this.

Would anyone use or prefer to be able to set time to unbillable by default?