While the loft bed is diametrically opposed to the futon bed and waterbed, it has many clear advantages. You can build it yourself from a few boards and slats, it saves a lot of room and features plenty of storage space. You can even put a desk under it. This makes it especially well suited for small 8 square meter rooms common in student housing.
But when it comes to sex, it is the last thing you should consider. Unless your ceiling is three meters high, you definitely should not get this type of bed. The problem is simple Ė a loft bed never has enough space to try anything more adventurous than spooning or the missionary position. While you may be able to pull off oral sex, that's about it. So stay away from the loft bed.