I think it is very dangerous when different folks are able to add/change/remove information from someone else's tree.  A couple of years ago I found some really awful errors on my family's tree that were apparently submitted/changed by someone I never heard of who is apparently an umpteenth cousin by marriage and whose knowledge is probably 4th hand at best. 

Chana Bonn
Philadelphia
Peresmyk, Appelbaum ,Feinglass - Pruzhany,Belarus
Kaplan, Gelburd, Kopman - Radiviliv, Ukraine (Radziwillow, Wolhynia)