I decided to try something new this year and place a few cameras around 6 to 7 feet in the air. I watched some research done on cameras at eye level for a deer and was amazed that deer sometimes do spook when they see the IRs go off. I bought three of the Bushnell HD 8MP cameras this year and with the quicker trigger spead than some of the older bushells I was confident I wouldn't have an issue getting pictures even at higher in the air. I'm quite happy with the results, I still have 1000's of pictures of deer and none looking at the camera which is very good to see. Plus, at the elevated level trespassers won't be able to see them as easy. I'm not saying that 3 to 4 feet is not a good height to keep them at, heck, I still keep about 5 or so at that level but was pleasantly surprised to see that 6 to 7 feet in the air works just as well.
Also, if your looking for a camera, I highly rec'd Bushnell HD Trophy Cam. You can pick them up for $150 now and are really great cameras. I have 9 right now and very impressed. I hear reconyx are great but the price tag is a little hard to swallow!