Out of Gamut ?
I recently designed a LO with some bright orangey-yellow colors which were picked up by my out-of-gamut warning. When I went to find substitute papers, I discovered that all of the bright orangey-yellow papers I had (including those from reputable designers) suffered from being out-of-gamut and then it dawned on me that no one could make an in-gamut paper in the color family I wanted.
From a user's (as opposed to a designer's), what's the downside in using out-of-gamut content in your LO's? I haven't routinely checked to see if my LO's are in gamut and I've been happy enough with the results printed as Shutterfly phtobooks.