Yeah, no kidding. Back in my younger and less persuasive days, we were on a project where we were forced by PHBs to use consumer drives in an enterprise system (storing and retreiving syslog data in a VERY busy environment). We were literally blowing them out every three months or so until the Powers That Be finally relented and let us put in proper storage (back then that also meant shelling out for a pricy SCSI HBA). I think that the gap has closed somewhat since then, and there are also some interesting options in drives that are purpose-built for things like DVRs and low-volume RAID. Also, back then (I don't know if it's still the case today) enterprise HDDs were tested individually for quality control, whereas consumer HDDs were just randomly sampled from each batch.
For many enterprise applications, though, the difference in things like seek times and sustained data transfer rate can be substantial in a busy environment.