According to Bitfinex, almost everyone uses MAX leverage:
"
1.We have decided to eliminate the “Choose your leverage” feature, i.e., 1:1, 2:1 & 2.5:1. Instead of this, we are implementing a “per-pair” leverage allowance. This will allow us to tailor the exposure based on the assets volatility. Virtually all users maximize this value, and since it is self-selected anyway, we have chosen to simplify our product by eliminating it."
couldn't that mean that everyone chooses 2.5:1 -- it was an option in user settings -- but not necessarily takes out a full margin position? i set mine to 2.5:1 but never did more than 1 or 1.5:1.