I used to work for a hospital that used this strategy for almost all of its internal reporting (I was contracted to ease the transition to Business Objects); it can get out of hand quickly.
Every morning between 8:45 and 9AM, doctors and administrators would come in, fire up Excel and refresh their data, the slowdown on the network was noticeable (pretty much a 'select *' on a massive de-normalised reporting tables hundreds of times throughout the site).
The flexibility that Excel offered some (not-too-technical) power users in those circumstances was fantastic, though, as much as I hate to admit it.
Every morning between 8:45 and 9AM, doctors and administrators would come in, fire up Excel and refresh their data, the slowdown on the network was noticeable (pretty much a 'select *' on a massive de-normalised reporting tables hundreds of times throughout the site).
The flexibility that Excel offered some (not-too-technical) power users in those circumstances was fantastic, though, as much as I hate to admit it.