John points out the intended difference between an "application" and a "service" but it turns out that this doesn't provide the necessary granularity. This was true of certain aD packages and will become more true as time goes on.
We really need to differentiate between mountable and non-mountable packages (and refuse to mount non-mountable ones that have no pages), and so-called "service" and "application" packages. Application packages will always be mountable but service packages may or may not.
The problem is that service packages frequently provide a small set of (typically) administration pages. There's nothing wrong with them doing this and for this reason such packages need to be mountable.
As far as the problem with procs being loaded or not depending on where you call it from, I've never seen that. John's pointed out some possible "gotchas" ...
