SUP is conceptually similar, except that instead of pinging a handful of well known feeds, SUP producers declare where their updates are available. Also, by using SUP-IDs instead of urls, the SUP feed is smaller, publishers can keep feeds private, and spam problems are eliminated (ping feeds are generally full of spam blogs). Briefly, SUP adds:

- Discoverability (feeds declare where they publish their updates)

- Privacy (SUP does not expose a site namespace or secret urls)

- Efficiency (each SUP entry is only about 20 bytes)

In practice, none of the feed based services other than the blogs use pinging services. Our hope is that with SUP we can get faster updates from the 42 non-blogging services that FriendFeed imports.

I think the difference here is that there's one feed for all users rather than a ping-per-user/blog