Many admins, same dream: Control the performance of the SharePoint Portal!!! Control and/ or eliminate the big performance killers for your System ( Beware – I don’t mean the biggest performance killer for every System: the end user! It’s a game, without them you can’t play it! ;-) ) is the first and best steps against phone calls like “Ohhhhh, MY Portal is soooo sloooooow!!”.
One of this performance killers in MOSS 2007 and WSS 3.0 are large lists and libraries. This means not only many items, but big items with many columns also.
Many Columns = Many rows in AllUserData Database per Item = bigger query = lower performance for every user using the same Content DB. Remember: all content from a Website Collection, maybe from one Web Application, is stored in the AllUserData Content. Right there the bottleneck for your Portal is hidden!! One large list locks your AllUserData table and every other request from other user from other subsites. And to make your Admionistrator's horror scenario complete: You can not prevent a user for executing a big request in 2007!
Take control with SharePoint 2010's Resource throttling settings! You can find the setting in the Central Administration under the Genral Setting of a Web Application.