Sure - I shoot 4x5 as my primary format, but occasionally use 5x7 and 8x10. This is for landscape photography, not portraiture, but some high-end portrait photographers also shoot large format. There's one who shoots 20x24 Polaroids!
Here's a photo of my primary camera if you'd like to see what it looks like (photo is indeed my own camera, not just the same model; it's part of a camera review on my website):
http://www.dannyburk.com/ebony_sv45u2.htm And no, it's not an antique, this model is in current production. I've had mine for nearly 11 years.
Re: film scanning, most home flatbeds will only accept sizes up to 4x5 or occasionally 5x7. There are pro flatbeds that take larger sizes. Drum scanners will take up to 8x10 (mine, for example), or some large ones can accept 11x14 negs. I just had someone write me last week to ask whether I could scan his 14x17 xray film; unfortunately I can't, so no sale there!