M Paul Lloyd wrote:What Channel 4 does is inject hard cash and manpower into a project that might otherwise be ignored.

They also provide a snapshot of what is going on at a particular site, which may then provoke further in-depth and long term investigation. In a good number of cases, the archaeological interest that called "Time Team" in, have carried on the dig as soon as the cameras have left.
It may not be text-book archaeology, but I think overall, "Time Team" have had a positive effect.
Knowledge comes, but wisdom lingers.