Thinking of Studying Mobile Social Media for Libraries

Okay, I'm in my second year of PhD studies and I still haven't settled on my exact research area let alone the research question.

So I need your - anybody's really - help in finding a good research area. So I'm wondering if anyone can provide me an example of mobile social media apps/sites. I'll get into the specifics...

Part of my problem is I have a lot of research interests, many of which fit well within the auspices of an Information program. The overall themes of my interests are user experience (including usability and accessibility), user participation (i.e. social media), and mobile media (specifically either a mobile website or mobile app.).

Within these areas I'm starting to look for a research problem. One domain that I think needs research is the user experience of mobile social media for libraries.

At this point, I'm defining my terms fairly broadly.

Mobile - I'm using it to indicate a device with Internet connection and input functionality. This includes smartphones (BlackBerry, iPhones, Androids, Nokia, etc.) and tablets (iPad, Blackberry's tablet.) I do not include e-Readers (eg.Kindle) as they have limited input functionality. I am not planning to include netbooks or laptops as although they can be quite small and portable they do not yet have the easy and quick access that mobile devices allow.

Social media - I'm defining this problem as any online content that allows users to add, edit, or share collectively. I'm not including tools that allow for individual customization.

Library - due to the newness of this area, I'm opening up my initial exploration from the now-common digital library to any bounded body of information on resources. Resources can be books, movies, journals, magazines, tv shows, bookmarks, etc.

So I would love to hear of any examples - and your opinions and experiences - with any mobile social media apps/sites for "libraries". (BTW, I'm not looking for libraries that have mobile apps/sites unless they have a social media component.)

I'm aware of (and love) some web library examples - such as LibraryThing, Zotero, Delicious, IMDB, Google Books, etc. But haven't encountered great examples in the mobile space. Any help in hastening my PhD studies would be greatly appreciated!