This is kind of redundant, because all these points have already been made, but YOUR ideal survival knife really depends on the circumstances YOU think you'll be employing that knife. Some of the comments have embedded assumptions that are not always explicitly stated, and much of the discussion has pointed out these assumptions.

I am in the camp of those whose DEFINITION of a survival knife is the knife you ALWAYS have with you when you make a conscious decision to be somewhere/do something that might put you in need of a knife for use as a survival tool.

When I go for a mountain bike ride in my local area, I don't expect to be in survival mode, and the knife I have with me (of course I have a knife with me) is just a small folder. I carry water, a small bike repair kit, maybe a power bar, and that's it!

When I go for an epic mountain bike ride in remote areas, I wear a small backpack and have my SR Howling Rat in there (or a similar sized fixed blade). I also have emergency rations, para cord, fire making stuff, etc. I've never had to survive using that stuff, but I have it just in case.

When I go backpacking at any time of year I have even more stuff, of course.

In winter I also carry extra layers of clothes, even more food, etc, even if it is a short excursion on xc skis or snowshoes in my own neighborhood, cuz winter can kill you around here if something happens. I still make a knife choice based on what tasks might be performed, but also on whether I want to carry something. I might go up to 5-6" blade in winter.

Everybody will make a different choice, depending on their circumstances, but the one thing a person should ask him/herself is DO YOU actually carry the knife you would prefer to have, or not? If not, then your preference is hypothetical <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />

I'm sure there are many folks here that have much more experience than I in survival situations, but I think reality is sometimes different than casual conversation.