A lot of the content we post on this blog is about social. Social is new, social is big, social is better (all true!) ... but, non-social is important too, and gadgets should behave gracefully when users have not enabled social features, or they aren't available. Not only is a large part of iGoogle's userbase not signed in, but when users add a new gadget to their pages, for the first time, it is always added without social features enabled. Users enable the social ACLs in a separate step, after the gadget has been added to the page.
Until they do that, the gadget will be rendered without social access - meaning that every single user will see your gadget without social access at least once. Plan for it! Make sure you can handle that case, even if you only display a message prompting users to sign in and enable social access so that your gadget can operate correctly.
For help with detecting whether a user's social functionality has been enabled and other iGoogle-specific OpenSocial questions, check out the Testing iGoogle State gadget. This cribsheet builds on the OpenSocial tutorial to provide a rapid way to look up example code for common social gadget tasks.
Many of the folks who contribute to OpenSocial and iGoogle will be at Google I/O in San Francisco on May 27-28. We love to talk about this stuff, so check out the Google I/O site to sign up and join us.