When I started this site last summer, I was toying with the idea of producing a terrabyte TiVo as a hacking project. It's not that I'd ever actually want that much space, I just wanted to see if it was possible. I explored it for a few days and there was an outside chance I could hack LBA48 support for larger hard drives into my old standalone TiVo, but I'd still have to mount two of the drives externally and figure out a way to split the IDE cables and still have enough juice in the power supply to keep it running. I scraped it because it wasn't really worth it.
But Sony's working on it, and the seven tuners part seems more outrageous than the amount of storage. If it will be recording HDTV content, a terabyte of storage will allow for a decent amount of content (50+ hours?) and is actually useful. Personally two tuners is great, and there's only been one or two instances where I wished I had one more tuner, but seven is ridiculous. I can't imagine what use case they designed a 7 tuner recorder for. I don't think there has ever been seven things on TV worth watching at once.