  Normalized free semi-circular random variables satisfy an upper Khintchine
inequality in $L_\infty$. We show that this implies the corresponding upper
Khintchine inequality in any noncommutative Banach function space. As
applications, we obtain a very simple proof of a well-known interpolation
result for row and column operator spaces and, moreover, answer an open
question on noncommutative moment inequalities concerning a paper by Bekjan and
Chen.
