user-identification

Prevent users from starting multiple accounts?

I know that in the end it, can't be done. But, what are the options to:   a) limit the options for persons to create multiple accounts,   b) increase the chance of detecting multiple accounts / person for a blog-like web service? (people can sign up for their own blog) Update: I think the 'limit the options' has been answered nic...

How does a website recognise me?

I've been using a chat website for a while (irrelevant which one), that has just "banned" me. I've never had to provide login detaisl of any sort, except a "nickname", which can be different every time you go on to the site. Now, irrespective of which ISP i'm on, or where geographically I'm located, or which browser I use ( IE or safari)...

How can I determine a user_id based on an email address in App Engine?

The newest App Engine SDK (1.2.1) has an API call to compute an ID for a user account based on his email address. (The ID remains the same even if the user changes his address later.) See this question about unique, opaque user IDs for information. However, I have a problem with this API call. user_id() works for logged-in users (i.e...

Documented solution for detection of users connecting with multiple screen names?

Say that I have a site where I want to detect users using multiple screen names, based on their connection data. I would want to detect them even if they are not using the multiple screen names simultaneously, but rather sequentially. Do you know of any documented method for doing this? ...

How to identify google forms user?

Hi, is there a way to know, who created an entry in a google spreadsheet via a form without giving them an account to our google apps domain? I am working a system to distribute users to different groups. first the users have to input there preferences the users are distributed between the groups with regard to some contraints like ...