Hey, Lenders stop taking account as collateral otherwise you will be tagged.
Vinsin pointed out a situation where you took control of an account to increase your chances of repayment and the whole transaction was out in the open, transparent for to the whole community to see. I have no objection to a lender operating as you have.
I do object to the use of the word "collateral" in such a situation. Collateral implies value, and in order for the account to have monetary value it would need to be sold to compensate for a defaulted loan. I think we all agree that selling accounts is a shady practice. As long as the lender doesn't see the account as having any monetary value and only uses it as leverage to increase his chances of getting repaid, I don't see anything wrong with the practice.
Even objects that are not sold can have value, sentimental value, accrued effort, status and reputation all of these can be considered reasons why an account is valued by its owner.
I do not believe holding accounts as collateral is against any forum rules, and lenders should be free to do so, if in their opinion it protects them against default. Obviously one must weigh up the risk of taking an account as collateral with the risk of them defaulting, hence the loan must be much lower than the perceived value of the account.