I define social intelligence as the ability to read cues, signals, body language and tone of voice of both others and yourself. The ability to navigate social situations by knowing the best way to respond, to detect insincerity, and being able to manipulate your own outward appearance to others is also a big part of it.
Personally, I view having a high social intelligence is very valueable in the real world. At least on the internet, some of the more common complaints/questions/challenges people seem to pose involve reading signals, socializing, etc. Now this could simply be selection bias (people who are socially awkward being more likely to ask for help/complain/vent on the internet vs people who are not ‘book smart’) or it could just be that social intelligence is much harder to develop than other kinds of intelligence. Navigating human interaction reminds me a lot of frustrations with the English language; often inconsistent, aspects that seem incredibly arbitrary and redundant, easy to pick up bad habits, difficult to perfect for many). Its an abstract skill you can’t simply develop by memorizing a lot of facts, and its usage and benefits can be much more subtle than being a good programmer, for example.
My wife has a tremendous amount of social intelligence, and it seems to benefit her in a lot of ways. In High School/College/Work she is very good at understanding what it is her teacher/supervisor/etc really wants/expects. My best friend is a very hard worker, but he burned himself out in his old IT job running around in circles chasing his tail trying to please his supervisors. My wife, in contrast, devoted her energies very efficiently at her job, putting the bulk of her effort on the things in her work that really mattered and abandoning the things that had no bearing/benefit to her task, happiness, and career. She seemed to ‘get’ people very quickly, and is very good at reading their intent. If she was ever interested enough in it, she’d probably be a great poker player because she is amazing at reading a person’s facial cues.
Things like Job interviews are one of her biggest strengths, and she’s never been unemployed since starting work in her early teens. She strongly believes that how you present yourself to someone along with your attitude goes a long way toward success, since even if you are some undiscovered genius you may not get very far with it if you can’t explain it well to people. While some people are obsessed with being ‘right’ about something, she’s more interested in getting people to accept that she’s right, which fosters a great deal of trust from her peers.
I brag about her a lot here, and I’ll own that, because I’m very proud of her and she’s had an extremely positive influence on my life. Simply observing how she interacts with people has improved the way I interact with people and I’m a lot better with patience, controlling my body language, tone of voice, etc. Sometimes making small improvements yields a lot of positive feedback from others (people taking you more seriously, more interested in what you have to say, more respectful of your boundaries). I took my own improvements and used it to better my relationship with my family, and now the relationship I have with my mom and brother (which over the years was the source of much griping on the SDMB) has improved tremendously.
For me, I value social intelligence because I feel like it can offset other weaknesses far more than having a ‘vulcan’ way of thinking and taking everything literally.