I had two experiences of frustration with search engines, in which they wouldn't do what I wanted.
The first was a Proquest (a newspaper archive) search on the word "supporter". Proquest searched for that word, but also included a synonym word "booster". The use of "booster" generated a great many hits, too many to wade through and not what I was looking for.
The second was Google Usenet in seeking the reference "90%". It dropped the "%" character and gave me all references to "90" which also gave a great many hits, too many to wade through.
In both examples I couldn't find any way to override.
As computers have become more advanced and used by untrained individuals, software intentionally has assists such as this built in. For example, MS Word will automatically convert as you type 1/2 to (the one-half character, ascii 171).
But as illustrated above, sometimes we don't want substitutions, we want exactly what we're looking for.
As a technical writer I often use technical acronyms. It is frustrating and irritating when typing to have software automatically "correct" things to something I don't want. I eventually figured out how to turn off the auto correct, but it was annoying. When I got a new release of the software, I had to learn new options and figure it out all over again. This is not productivity, but a hinderance. Before I resolve this, I was so frustrated I turned off the PC and used a plain typewriter for my writeup. (I am worried about Vista which is supposed to be very different).
The lesson for those who design such software is to be real careful when you start assuming what your users really are seeking. Some auto fixes are ok, but there should always be an EASY option to use a literal as a literal.
Back in the 1960s auto makers built cars with lots of chrome, wraparound glass, and little gadgets. They were desperate to add glitz and glamour to sell more cars. The curve glass actually made visibility worse, the chrome would fall off or cause sun glare, and the gadgets would soon break and be worthless. The industry ended up under nasty attack (Ralph Nader's book).
This is a lesson for today's software and hardware industry. You sure don't want an articulate critic writing a popular book "Unsafe at any speed" about computers. The youngers who develop this stuff are too young to remember the attacks on autos. Further, as computerization increased in the 1960s, many people resented being reduced to a punch card "do not fold staple or mutilate"; popular writers criticized computers.
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