I still don’t understand why email would go through the handset manufacturer’s servers? My email goes from GMail to my HTC phone without touching HTC’s system so the only way it stops working is if AT&T’s data network goes down or GMail goes down. Why would anyone buy a handset that requires you to add a 3rd breaking point to that equation? Not to mention the privacy issues of sending your email through a company that has no reason to see it.

My iPhone e-mail goes directly from my corporate Exchange server to my iPhone using IMAP4 industry standards.

One would think that “security experts” might appreciate such level of security.

Blackberry phones are controlled extensively through the Blackberry servers. All data services and even picture messaging require a subscription to the blackberry service. This has its advantages, 1 set of settings for everything, a standard platorm across networks allowing easy transfer of data, independent access point for uninterupted data transfer (voice calls take president over data calls) the downside to all this is that it costs a subscription fee (£10/month on uk networks).
using an enterprise server with blackberries does not do this, the access goes straight through your email server also allows you to instantly synchronise your contacts/calander etc, this also alows you to set access permissions from the corporate server etc.
this is more cash for the subscription, plus the cost of the servers software, licenses etc.
I prefer htc phones myself, or my trusty sony ericsson k800i. so to answer your question, its a way of making people pay RIM lots of money for a phone.

I forgot to add, emails are no longer stored by RIM on any server, they are merely transported through them to the phone.