Personally i agree with account sharing on a "basic level" so to speak.
I occasionally let my little bro try characters out on my account but its never in ranked or anything. in fact it's usually just a custom game but i honestly don't see the problem with sharing an account like that. Being on someone else's account that you don't know however, whether it be sold accounts, hacking, boosting, etc. should still definitely be punished.
The problem i see would be figuring out whats really going on with the account and punishing appropriately.
I mean it really doesnt affect anything if your friend uses an account just because he wants to try out a skin that he/she doesnt have, and see if they like it...
EDIT: Opens a thread for legit discussion> Gets down-voted
wonder why the league comunity has such a bad reputation, even you idiots contribute to it, its so bad that even the boards are filled with weaboos that upvote "you want a cookie? ill give you a cookie xD" posts and down votes legitimate threads... what are you guys , 10 year olds?