Please see below for advice from the Yorkshire & Humber Grid for Learning concerning Formspring:-

YHGfL have recently responded to some concerns around Formspring 

Formspring is a social networking site which lets users set up a profile and enables them to post questions to other users. It can be integrated with other social networking sites such as Facebook and information sharing sites like Twitter , so these questions can appear on profiles set up on these sites. Recently it has been used by certain users to cyberbully and harass, so Formspring have made changes to their settings in order that users can choose not to receive anonymous questions.

Full details of how to do this appear in this booklet.