Most devices these days including the iPad and things like Go Pros film in at least 720P which absolutely fills up storage space in no time at all. I started filming my kids' sporting events in HD and editing them on my laptop and I completely filled up 1 terabyte of storage on my computer in no time at all. Then I had to start playing the game of moving older stuff to external storage which totally sucks if you want to go back to it quickly. 1 minute of 1080P video at 60fps is around 200MB depending on the format, an hour is like 12 gigs. The only reasonable way to manage almost any amount of HD video is on a desktop system with loads of cheap(er) storage.
Well yeah, for bulk video storage you could eat 2TB easily. Active files for an editing project at 1080P, especially if you're weeding through footage after each day of shooting (if you don't, you'll go nuts later), 512GB should be OK.
