Screenshot of my Public Notes profile at kindle.amazon.com

Amazon’s “Public Notes” feature for Kindle has been available for months. So why did my following and follower counts rocket up overnight to five times what they had been?

It’s simple. When kindle.amazon.com was introduced in February, you had to manually add users you wanted to follow. Now, if you’ve linked your Twitter or Facebook accounts to Public Notes, you automatically follow other connected users that you follow on those networks.

The old way was a bit of a crapshoot — it was hard to find and add other people unless they explicitly advertised their accounts or began broadcasting their highlights and marginalia on their blogs or social media.

The new way is a little bit creepy — particularly since there doesn’t seem to have been any announcement from Amazon that they were changing how social media links were going to be used. (Amazon representatives haven’t responded to my requests for comment.)

Screenshot of the "Link Account" configuration page at kindle.amazon.com

It’s also a little bit creepy that the default for linking social media networks is set to broadcast your Public Notes activity on those networks to all your friends and followers. That option at least can be shut off; auto-adding the people you follow can’t. If you link your Kindle public notes to Twitter or Facebook because you would occasionally like to share a passage or note from a book you’re reading, you’re stuck auto-following everybody else who wants to do the same.

As a convenience, whenever a Facebook friend starts to use kindle.amazon.com, or you become friends on Facebook with someone who already uses kindle.amazon.com, we’ll make sure that you follow them here too.

Again, for some people this may be perfectly convenient: There’s no need to rebuild your social graph from scratch on yet another social network. It makes Kindle Public Notes the perfect set-it-and-forget-it special-purpose social network. All you have to choose is which of your books’ notes, highlights and reading status you wish to make public or keep private.

But it’s worth noting that Barnes & Noble took precisely the opposite approach with Nook Friends. On the Nook and Nook Color, you can share with third-party social media like Twitter or Facebook, or you can share with B&N’s Nook Friends, but the networks are completely sandboxed from one another. When I interviewed Barnes & Noble representatives in April, they were explicit on this point: Nobody would be auto-added to your social network. Every friend request would have to be separately initiated and approved.

Remember, Nook Friends launched shortly after Google settled a federal case over its rollout of Buzz, which used e-mail contacts to build a public social network without clear notification.

I’m not entirely sure where Amazon’s use of Twitter and Facebook to do the same rates on that scale. All my Twitter follows and followers are public, and I have technically authorized Amazon and Twitter to share information. Facebook users are promised a little bit more privacy with their contacts. I think they might have more reason to be upset if huge chunks of their social graph have been made public.

The sudden addition of new people also makes your network look pretty strange. Many people never filled out their Public Notes profiles, or filled it out with phony info. Many people on my following list are now listed only as “Unknown” — their only identifying characteristic is their linked Twitter account. They clearly did not expect their profiles would become visible to dozens of extra followers overnight.

Bootstrapping Public Notes with Twitter and Facebook makes a lot of sense for Amazon. It makes the network easier to start using and has certainly increased its visibility. Many people, including reporters covering e-readers and social media, believed it was a brand-new service that had sprung up overnight.

It needs this visibility, in part because it’s not a full-fledged social network. It can’t do e-book-lending like Nook Friends, catalog non-Amazon books like LibraryThing, or facilitate book groups and discussion like Goodreads. It’s lightweight — the Twitter to its competitors’ Google+, LinkedIn and Facebook.

I like using Kindle’s Public Notes quite a bit, maybe even more for newspapers and magazines than books, and I’m excited that more of my social media friends may be using it. But next time, Amazon — could you please at least give us all a little more of a heads-up?