Hi Mario,
I belong to several yahoo groups and I believe most allow me to post my own photos, files as well as links to my own website. It sure is handy to have that flexibility. I have been a member of some for many years and don't remember any issues with abuse of the posting ability of any member. I am sure the potential is there though and can understand why the moderators and owners closely control what can be posted, but is is unhandy and inconvenient, but the groups are provided at no cost to us so we accept some inconvenience.
Dick