1280x720 is a good delivery resolution for YouTube,
but does not necessarily reflect the acquisition resolution.
Top shelf productions will generally be shot in the highest possible resolution.
The minimum would be at least full HD (1920x1080), and quite possibly even
beyond that (RED 4K is 4096x2304).
That said... I have seen some really good stuff shot and edited at 720p.
A large part of this decision is what sort of production it will be...
gritty realism and heavy effects and compositing may require different acquisition formats.
It is not unusual (especially in music videos) to see mixed formats in the same piece.
The apposite word being some. Film remains in use, but in the music sector almost entirely for 'artistic' purposes. Aside from IMAX the technical performance and ease of use of digital exceeds emulsion, as pretty much everything is edited and shown digitally it's not the size of the film grains that matter, it's the effective resolution after telecine - most 35mm stock is scanned for production at 1080 so you may as well just shoot digital at the same spec. Go back a couple of years and shooting in 2K or 4K was a nightmare (the early REDs were petulant to say the least) but with new mass-production rigs like the C300 it's just as reliable as shooting with a camcorder.
In answer to the original question, a music video that will be distributed to air via services such as Fastrax really can't be below 1080i, but beyond that it depends entirely on your budget and the look you're after. If you record in 720 you'll be limited to standard-def TV and online channels; no major label would fund a shoot that'll be rejected by HD broadcasters. An indie band might only want a YouTube video, but these days it's very rare to find cameras on a pro shoot that'll only record 720 (even bullet cams and super-high-speed units shoot at 1080). Provided you have a decent spec machine, Premiere Pro doesn't care what you give it and has class-leading abilities to mix and match footage from different cameras on the same timeline, but you can't upscale original footage without losing quality so it's always best to start as big as you can. The choice of camera depends on the look and post-production you want (DSLR gives shallow depth of field, but it's a nightmare to chroma key unless you record direct from the sensor).
The advantages of shooting over your intended maximum output resolution are beyond the scope of these forums, but include log format files, full color depth, the ability to pan and crop the frame, and future-proofing the material. There's a financial cost in shooting over 1080 (compare the hire costs of a DSLR over a RED or C300, plus the lenses) but for a major artist that's nothing in the overall scheme of things. Remember that there are three points where you decide the resolution - when you shoot, when you edit, and when you export - it's very common to shoot and edit in 2K or 4K, but export at 1080i or lower for Web targeting, as if someone wants a 2K version next year you just have to press Export again. Offline editing capabilities in Premiere Pro mean you can edit the sequence using low-res proxies, reading the original footage only when rendering the final export, so you don't necessarily need a supercomputer to work with RED (but it helps!).
That's not to say you can't shoot entirely in 1080 (e.g. on a DSLR) and many people use them, but you lose the flexibility I mention above. If you're paying for a set and crew for a 3-day shoot, saving a few hundred bucks on camera hire will come back and haunt you. If the label's paying, their lawyers will haunt you.
Jim Curtis wrote:
Joe is right. And some are even shot on a format called "film."