not only for surfers, but for advertisers as well. If advertisers, do not know this fact, they have not understood an important part of the digital branding / Ad game.
Searching for persons with dyslexia may be a very important topic:
http://www.interdys.org/
http://www.dyslexiatalk.com/
Sitesearch is in my view getting too less information, eg on sites found on these links
http://univ.cc/
http://www.google.com/options/universities.html
http://www.google.com/unclesam
Obvious reason: Not profitable (Ad driven).
Related link:
http://daphne.palomar.edu/tgsearch/