Just yesterday I had a discussion regarding Skilled Performance. I argued that we should normalize certain data to have it look like the same for the user. It was argued against that, stating that if a user enters data in a certain way, she would want it to appear in that exact way. Even if this might be true, which I doubt - it is about tags [as in folksonomy] and the people who will enter the tags don't know Jack about tagging, least to say about web navigation or web usability- the chance that the customer actually using the tags will understand why one time a tag in all lowercase and one time spelled grammatically correct is even slimmer. So I advised that we should normalize all tags in the customer views to be either all lower-case or, what I'd prefer given the nature of the application, to start with an upper-case letter and continue lower-case.
Interstingly enough Nielsen just happened to write in his last Alert Box (emphasis mine):
Skilled performance almost never happens on the Web, because users constantly encounter new pages; that is, they spend most of their time pondering options and trying to understand the content that's being presented. [Quelle]
This thought fits in well with Krugs "Don't make me think" pattern: Don't distract the user more than you have to to make the application work.