You can drag a photo to e-mail; download a photo to email; drag a photo to a document. But to post on a form it needs to be "digitilized" for some reason. ergo these photo sites. Maybe Dave can create a proprietary one for this site.
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My understanding is the problem is digital storage space and therefore cost for the person or organization running the forum. If Dave wanted to add servers that had sufficient storage capacity then we'd be good to go. I believe these hosting sites got started when data storage was relatively costly. Comparatively now, it's staggeringly cheap.