Facebook is very much well-renowned as a social networking site. This site caters to a big market ranging from teenagers to adults.
When asked why they are Facebook aficionados, many would mention interesting features, such as interactivity, web-based games (Pet Society, Farmtown, Restaurant City, etc.), and random quizzes and exams for everyone.
As for me, I have another special reason why I visit Facebook.
I avail of the service uLink.
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Chikka, by far, is more advanced and commercialized. However, uLink timidly caters to my SMS needs. Yes, Free SMS on Facebook is what I'm after for. :) Without having to download anything, just be a registered Facebook user, and pronto! You can send Free SMS.
Facebook, after all, allows interactivity and provides satisfactory embedded services for its users.