About: http://webisa.webdatacommons.org/17591983

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Most of such sites will require you to reset password by mail anyway, so they will need your email info to get anywhere, the answer is mostly to prevent people from annoying you by constantly resetting the password.
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com