How much of a visual metaphore does a logo have to be? If you sell fire extinguishers, does your logo have to include fire? If you service lifts, does your logo need an up and down arrow? Maybe less is more and we don't need to try so hard.
Looking at the most successful brand logos, there's often little to convey any physical product or service. Obviously many of the examples above have the benefit of decades of brand awareness - but if we want our logos to sit happily with these we may need to embrace a "less is more" approach.