Saying this will hurt users is like saying gasoline will hurt a car since it could ignite. Obviously take care of it, and it will obviously improve your users experience.
I read through the spec a little[0], the thing with this attribute that I'm worried about is if the page is rendered or of scripts are executed. If they are (mainly scripts) then you could see a legitimate website become attacked and have these placed in without anyone knowing or detecting for possibly several days.<p><pre><code> [0]: http://www.w3.org/TR/REC-html40/types.html#type-links</code></pre>
It seems like something new to check for on your DB heavy pages. You could ignore requests with that header if your servers can't handle the additional traffic.