If you're investing by purchasing the item, then yes, you can only lose 100%. However, if you pay the current rate ( + lending fee ) to borrow a BTC to sell expecting that when you go to repay the BTC you'll be able to purchase one at a much lower rate due to a bubble popping, thus banking the difference, and instead the cost raises exponentially, it could cost you considerably more than 100% of the amount you initially invested when borrowing the initial-sale BTC to buy the BTC you need to replace it.

That is, yes for long positions, no for short sales.