col:
I seem to recollect reading somewhere that the wake turbulence of significantly smaller aircraft (757?) were somewhat underestimated at the time of development, and that it's a complex issue to say the least.
Yes it certainly is! The wake of the 757 has been discussed many times in various forums here and you should be able to find some by searching. It has an unusual wake for it's size but the reasons are now well known. I'm not sure if this means that future designs will change.