The reason I don't "buy" having to pass thru RIM is in the past when nextel has problems with their email to berry's, we were not effected cause we don't the nextel/rim server infrastructure as our server.
Email from blackberry works this way (if you are using MS Exchange):
Blackberry->wireless carrier->RIM->BES->MS Exchange Server->Internet
Email to blackberry works this way:
Internet->MS Exchange Server->BES->RIM->wireless carrier->blackberry
Your Exchange server down: only your company impacted.
Wireless carrier network down: only subscribers using this network impacted.
RIM is down: all blackberries impacted.
You "not buying" that fact is the proof RIM runs damn good infrastructure which goes down very, very infrequently. Infrequently enough not to notice it exists. This is the way we like it.