At least with SSDs, there's much less worry about your RAID 5/6 array self-destructing while it's failing over to a hot spare. With hard drives of that size, I'd only feel comfortable with full mirroring.
But RAID6 is still popular, among crazier folk.
And RAID6 with SSDs screams. And rebuilds fast.
Currently I'm at a small-ish startup and I have ~150 TB of data on a synology nas. It's in 2 raid groups, both raid 6. Seemed safe enough.
edit Ah, right. From some reason I didn't make the connection that raid 10 was raid 0+1, it doesn't work for us simple because of the sheer amount of data we need to store. Also, although it would be a real bitch if we lost everything(like set us back a week+), most of the data is derived data, and we have all the raw data in cold storage, so we could eventually rebuild the array from scratch.