The Agility Alliance has come out and said that Linux should not be used in the enterprise. Of course every vendor represented in this list has something to lose if Linux takes off in the enterprise, so it's no surprise they're making waves at this point. I'm sure the same was said of UNIX when it made it's enterprise debut, and possibly Microsoft Windows (but we're still saying it shouldn't be used in the enterprise, and apparently no-one is listening. :) )