I was recently working with a person via email to offer some help in the setting up of their Project Server environment. It was a friend of a friend that worked for a nonprofit and so I was donating time to fill in the gaps they had in understanding a few of the finer points. Anyway, one of their goals for deploying Project Server was to "better manage the time of their staff." A laudable goal to be sure, right? Well recently, after they had the deployment underway I got an email talking about how the resources were revolting against the system. I talked a bit about how things were going and asked some questions about how they were using the system. It turns out that the deployment of Project Server helped them see that many of their resources were not 100% utilized, not even close and many were only working on one project while also being "underutilized". Well they soon fixed this and there were some resources that now had 30 or 40 (one had 75) tasks A WEEK across as many as 10 different projects! (in a single week!)
I told him that revolt was not bad and that he was lucky the resources did not band together and have him killed! These resources went from working on 1 or maybe 2 or 3 projects at a time to working on an average of 7 projects in any given week.
I had to explain to my friend the evils not only in assigning anyone at a full 100% for extended periods of time but also the evils of having someone do work on that many different projects at the same time. I referred him to the August 2003 Software Development Magazine article on task switching/multi-tasking by product management guru Johanna Rothman. She does a great job of discussing why continual context switching is a bad thing.
Nobody should be assigned to work on 8 projects at a time and if it MUST be done it should only be for a very short period of time. Johanna talks about the cost of this in terms of time but there is another cost to this and that is the toll this kind of switching has one the morale of your resources. It is draining physically and mentally to have to move between so many different projects. The other factor that comes in is that if there are 6 or 8 project managers in this persons life there is no way they are not being pressured to give one project more time than has been allotted in this complex assignments scheme. Each project manager has only been given a small fraction of that person's time. You KNOW that at least one is sending that person email asking for more time "under the table". Nobody will fess-up but you have to know it is happening. :-)
Do you best to consolidate the assignments on different projects so that they can be done in chunks that require a whole person or at least as much of a whole person as possible. You will get better work out of your resources and you can just a little more sure that they are not plotting your death. :-)