MPLS VPN design - RR in forwarding path?

[notify at marcinkurek.com (Marcin Kurek)]

Hi everyone,

I'm reading Randy's Zhang BGP Design and Implementation and I found 
following guidelines about designing RR-based MPLS VPN architecture:
- Partition RRs
- Move RRs out of the forwarding path
- Use a high-end processor with maximum memory
- Use peer groups
- Tune RR routers for improved performance.

Since the book is a bit outdated (2004) I'm curious if these rules still 
apply to modern SP networks.
What would be the reasoning behind keeping RRs out of the forwarding 
path? Is it only a matter of performance and stability?

Thanks,
Marcin