Since this is something you have to choose to turn on. Is there any reason why I would not want to turn it on?
 
Advantage Disadvantages? Are the reasons Server load? and Compatibility?

Greetings
 
Main issue relates to - encryption' option there won't be any possibility to restore passwords but only to set new ones.
 
For this reason choice carefully..Its not uncommon for customers to forget their password to reduce added burden on a returning customer we use non-encrypted on our sites. But, we also do not collect or store credit card info.
 
 
Tony
www.holleyland.com/viart

I would say always use it, if they forget a password its much safer to make a new one instead of store peoples passwords unencrypted. People tend to use the same passwords on multiple sites.