Here is an interesting quote from the texasbigfoot.com site.
"Here are my reasons for all the failures (to capture proof):
1. No one is spending enough time in the woods on the search,
2. Not many know what to do in searching, overlooking things, or vice-versa, seeing things that aren't significant to the task,
3. There are not many of these animals around,
4. They, like most animals who live in the forest, know how to camouflage themselves quickly and easily,
5. Most encounters with humans are probably mistakes on the part of the Bigfoot, yet researchers are trying to fill in the picture with them as to being something significant.
– Rick Noll "
My comments,
1. It is not the time spent looking that matters, it is the time spent listening that matters.
2. Full agreement. Search with your ears, not with your eyes
3. Actually, there appear to be millions of them.
4. Can't beat good old fashioned invisibility for camoflage
5. The mistake being, playing around in our dimension, when humans were present.