Back to the 720p thing.
Apparently, at 1080p and high frame rates memory cards tend to overheat badly when shooting longer scenes. I'm sure the smaller bodies of DSLRs contribute to card heating as well.
At 720p my cards do still tend to heat up quite nicely when shooting video.
According lore all or almost all of "The Avengers" was shot using Canon 7D and 5D and 1D DSLRs.
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