I've done this a number of times, and have actually had cager folk say that is what that space should be used for anyway. I figure a)why take up a whole spot for just my bike, b) it keeps the bike from being run over when some unattentive cager flies into the space shrouded by cars on either side, c) so long as I put it someplace that's not in the way of any sort of door swing, adjacent to a handicapped spot, or impedes the line of sight when turning out of the aisle, there's little harm in it.