[tenpa0000]

The flip side is enumerable IDs. Back when I was scraping a site for a side project, sequential photo IDs were basically a free sitemap. YouTube's random-ish IDs aren't just branding — they at least make bulk harvesting annoying.

[jeffbee]

You cannot afford to "bulk harvest" YouTube.

[Yolopix]

Bulk harvesting doesn't necessarily mean downloading every video, there is still useful metadata. But in this case non-enumerable IDs are on purpose, it would defeat the "unlisted video" system.