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I think it'd be useful to have a list of suggested sites on which to host images (e.g. diagrams) used in questions and answer.
Imgur (extension for Chrome)
Stack Exchange's internal image uploader
Disallow new embedded images from hosts other than the SE imgur account
Why does Stack Exchange use Imgur to host images?
Dropbox (use its public folder feature)
Link with referral (+250 MB)
imgFTW (extension for Chrome)