If your estimated gain is more than the lender's interest rate, you can say it is a very useful situtaion to borrow bitcoins.
But then borrowing bitcoins or borrowing money from bank is no different than each other, while except this forum is full with scammers, banks are usually safe.
Tldr; I wouldn't borrow or lend any btc's in this forum. Too risky.
I think borrow anything from any one is break the relation from others. So try to get as like as gift or buy on the situation. If any of us going to borrow and can't return on time it will break up tour relation.