It's great that Leanpub makes it so easy to register, but it would be even better if you didn't have to. I don't want to provide my email address to download a file. I used a disposable one and I'm sure some others did, too. That's just going to add (a tiny bit of) work for the Leanpub email server and make their stats look a little better than they really are.
Also, the site creating a "profile" for me when all I did was download a book makes me feel "sucked in" a little. I know, rationally, that there's really no downside to it for me, but I still can't shake the feeling that this is more than I agreed to.
Part of the rationale is that this is how you can access updates: I notify my readers when I add a new essay to the book through leanpub: I don't see your address or any other info, but leanpub forwards my message to the book's readers as an email.
Also, the site creating a "profile" for me when all I did was download a book makes me feel "sucked in" a little. I know, rationally, that there's really no downside to it for me, but I still can't shake the feeling that this is more than I agreed to.