Lending btc is also a good business these days in Poloniex.
Etherium traders are eating so much btc that the rates are ridiculous.
0.2 % a day turns to be over 70 % annually and I am not even calculating the compounded interests which makes it attractive to give out only 2 day loans.
I am not recommending anyone holding margin long positions in XMR these days. That's only a way to lose XMR as the lenders make nice money out of the long positions.
Holding short positions may not be smart either.
Going long on margin always seems like a bad idea. It's like getting that couch from RentACenter where you only need to pay $19.99/mo for the rest of your life...
Accumulate XMR the right way - buy what you can afford.
I do not know if it is always a bad idea for having a margin long for XMR.
In order to be profitable/to make sense having long position, the interest rate should be lower than the average price growth rate. It somewhat made sense when btc rates were like 0.03-0.04 % per day but certainly 0.25 % per day is pure ripping off especially these days as Monero is moving nothing but sideways.
Having a margin long position under the current circumstances is very strong view for almost immediate and quick rise which probably will not happen unless something sudden and good happens which creates a spike on the demand of Monero, but those events I would consider black swans. Sometimes they happen but usually not.
I think Monero is in quite slow rising channel. However, the lower bounds are rising constantly and it will eventually force either breaking the rising pattern into bearish or breaking out to higher levels. I hope the latter.