Citing increased adoption of S-DVR over CCTV as a video capture mechanism in many businesses or other places needing security cameras, Seagate is introducing higher capacities of the SV35 and the Barracuda “ES” and “EE25” series drives. They are manufactured specifically for continuous use and “rugged” operation:
Seagate’s broad portfolio of surveillance-optimized hard drives include the Seagate SV35 Series, the Seagate Barracuda ES and the Seagate EE25 Series. All of these hard drives are engineered for continuous use and provide the utmost reliability, ruggedness and capacity.
How that would differ from a server-class drive I don't know, excepting perhaps the “rugged” operation aspect. Regardless, the newer units such as the SV35 have capacities up to 1TB, and units like the EE25 series are built to withstand extreme environmental conditions such as extreme temperatures, high humidity, shock or vibration, such as you might find in a damp mall security closet.
Hard drives clearly have an advantage over tape when it comes to storage density – a 1TB HDD can carry a lot more VHS-quality video than could a stack of VHS tapes – but reliability still is a big concern for any DVR system that a bank or a mall might rely on. Seagate is obviously trying to tell people that you can trust modern drives to be superior to tapes in that aspect. You can read the full press release at Seagate's site.