When I think of the various affordances that social media have to offer, I repeatedly return to the question- no doubt because of the techno-phobe in me- ‘Who actually needs to do that?’ But as discussed on the wiki page, individual variables will play a crucial role in how and whether someone will take advantage of a given technology’s affordances. It is interesting to note that research has been done that links certain affordances with particular personality traits.
For example, Reid and Reid (2010) identified two very real but hidden 
affordances of SMS messaging. First, the lag between responses allows interlocutors to carefully craft their message “to achieve important self-presentational goals, free from the multiple distractions of real-time social interaction” (p. 5). According to various reports, this expressive control fosters a confidence that texters lack with more immediate ways of communicating. On the other hand, SMS also allows users to engage in near-synchronous interaction with one another (extended conversational involvement). A number of the very basic functions of SMS support these two affordances. According to their survey research, the young, single, and socially anxious were more likely to benefit from these affordances. As the researchers note, this study has relevance for the deeper debate about the relationship between technology (and the internet in particular) and social withdrawal. Its results contradict theories that the socially withdrawn become more so with use of the internet, while only the extroverted will see the benefits. Texters who were able to notice and exploit the expressive and interactive affordances of SMS were thereby able to increase their social interaction.
This article is intuitively appealing on a number of levels. It is certainly in accordance with my own experience with cell phones; the SMS is a valuable tool I’ve used in the past to overcome shyness, particularly when communicating with people I don’t know well. But more importantly, it clarifies for me the difference between affordances and functions, while illustrating how the former can be actually ‘constructed’ by certain users. It would seem that the concept of affordances is important for measuring the worth of new technology.
Reid, F., & Reid, D. (2010). The expressive and conversational affordances of mobile messaging. Behaviour & Information Technology, 29(1), 3-22. doi:10.1080/01449290701497079.
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closeup sms http://www.sxc.hu/photo/649115