Well, it does indeed appear that some programs that load before tbbMeter starts up will not have any of their network activity recognised.
A follow-up question then; is there any way to ensure tbbMeter starts first? I suspect this may be tricky, as tbbMeter runs as a service, and most of my programs which run at startup that access the Internet do not.
Failing that, are there any plans for a future version of tbbMeter to work around this issue? I quite like how it works generally, and I'd hate to have to consider looking for an alternative for the sake of a problem which is, essentially, just a bit of a nuisance.