I used to think it was always my job to make forms and interfaces as unobtrusive as possible. More recently, I've realized it is sometimes necessary to slow the user down (within reason) especially when I want them to stop and pay attention to something that is crucial.
I've recently been presented with a challenge with a client who makes his revenue off the obtrusive ads on the site. I'm not a financial guy, so my first reflex is to clean up the ad space, and get the users right to their content. On his end, it's the entire point to put the ads "in the way" of where the user would expect to see their search results.
Of course, surprising the user in this way goes against everything I believe in as far as UI/UX goes. This clients' site is used in a way that users come searching for one thing, get it, and leave. Given this business model, what kinds of UX improvements don't undermine his bottom line?