In my opinion, the external connection to the internet is less important than fat pipes inside the premises. I’m not concerned that users can get to Facebook quickly. I am concerned that users can get to spindles in the server room quickly. If you start adding video for any reason (staff development, conference calling, etc.) in any sort of multi-cast or potential multi-cast situation, the bandwidth will get sucked up at some point down the road.
Most Gb gear today has the added dimension of creating an even faster backbone when necessary. Almost all the Avaya gear can accept a 10 Gb GBIC to provide huge pipes when needed. Also, if you’ve got any WAN needs on fiber, you can easily upgrade to 10Gb and start spreading your off-site backups and DR applications to another corner of the campus. I’m envisioning a complete data center running VM’s of all essential services at the “off-site”. When the off-site is in production, I don’t wawnt bandwidth limitations impacting my efforts or user productivity. As I said in another post - it is a financial decision. If you can rationalize it all, it is worth the trouble now to avoid another upgrade in 5 years. The industry will catch up to overly sized pipes that you implement today.