I see a number of issues holding professionals back from contributing:
1) Some do not realize that it is possible to edit Wikipedia ( I hear this
at work when people ask me how I became an editor ). Maybe we should
advertise the fact that yes you too can edit Wikipedia.
2) Many are just not interested. In medicine we have had issues with
getting physicians to do continuing medical education. Many just want to do
their job and that is it. Contributing to Wikipedia is work. However
students are required to do work and I think this is one of the populations
which would be easiest to attract. McGill University may have started a
Wikipedia club. Promoting these may be useful.
3) A great deal of competition to Wikipedia has sprung up such as
Radiopeadia ( which does not allow commercial use of images ), Medpedia (
which only allow professionals to contribute ), and Wikidocs ( which has
more technical content ). Each addressing some perceived drawback in
Wikipedia. None however has received the viewership of Wikipedia but of
course cuts into the pool of available volunteers. Medpedia has partnered
with a number of very respected Universities. I think we could learn
something for each of these formats such as clarification around image
copyright and that CC does not mean you lose the rights to it, greater
exposure of the professionals who already contribute, etc.
4) Wikipedia has received negative press in professional publications. We
need to address these negativities most of which are false. Currently a
number of us at WikiProject Med are writing a paper for publication
promoting Wikipedia as a health care information resource. Other subject
areas should do the same.