Something that kind of bugs me is the following. Which can be patched each time, customer accounts are set to per website view.
Have a POS store and the Online Store as 2 different websites setup.
Due to reward points and customer credit, when creating an admin order you will want to select the customer account associated to the online store website.
Placing the order using the POS website creates a new customer account (even though I've selected the Online Store account)
The point is I guess.... Why would you want it to create a new customer account, even though you've selected an account. The login behind this is strange and existed for a looooonggg time.
Yes it needs to be setup as per website for accounts due to the fact that normally these sites are multi stores and don't want customers having global accounts.
So, why keep including the logic to create a new customer account if a customer account has been selected.
On a side note, if a customer account has already been created for POS and the Online Store view is selected for the customer. You'll get "email already exists" error because it's trying to create another account for POS.