I often see people use words in square brackets as part of the question title, such as:
[iphone] can't display frobnicator after doohickey
how to round a number to two decimal places [c++]
Naturally, when the asker is prompted to enter tags for their question, they'll typically just use the same words. This is redundant, as Stack Overflow has tags for this very purpose (and they work better for searching and categorisation than bracketed words in the title).
Suggestion: On the "Ask Question" page, when the title is typed using words in square brackets like the above, automatically remove the words from the title and pre-populate the tag entry field.