There are other important search engines out there like baidu. I think it is also important to optimize site in those kind of SE.
no it wont profit blade, if the other 5% doesnt already want to use the top 3, then i dont think optimizing would help. also, mighty mouse, where did you get the information i think it is incorrect
every little bit helps, you never know when you might get lucky, if it doesn't take too much time, i think it's not bad to optimize for everything.
There are a billion internet users in the world, so 5% is like 50 million people who use alternate search engines. Still a lot.
Its a niche like any other. If enough people ignore it then there is little competition and it can easier to grab a high percentage of low competition traffic rather then fighting for a tiny share of the more competitive traffic.
personaly i feel that every little bit help if you got a site with 10,s of thousands of visitores a week then that smale percentage would be alot and alot of revnue.
If you have a very large website that is fully optimized for the three kings already, then why not go after the little guys too? The more traffic the better, even if it is only a small amount.