I've yet to create a Facebook or Twitter account to delete. Well... I made a twitter account the other day solely to find out what happened to 2mooglesgaming, I'll never use it again though.
I first learned and heard about social networking tools in high school, at that time everyone was using MSN messenger, IRC, Myspace and Bebo. I think Bebo may have been more popular in the UK as whenever people talk about old social networks online it's usually Myspace.
I was introduced to MSN messenger first which was pretty neat, I could hold long conversations with friends on a full size keyboard and it wouldn't cost me a penny, back then the only alternative to conversing with friends was texting with that horrid 123 keyboard... oh and you could like hang out with them in reality and maybe call them but this was 2000-2006 not the 1960's.
Then came my introduction to social networking websites Bebo and Myspace. Now I don't hate my High School experience, it had its ups and downs, but it has to be one of the most irritating periods in anyone's life, with it's cliques, caste system, and general egotism mounted onto stupidity, naturally this isn't going to transfer well onto a web page, and it didn't. For a long time my early experience of social networking sites jaded my general outlook on them.
It's only been a couple of years since I've thought of social networks a little more positively. I can see now that it helps bring communities together when it's not always possible to work physically close to one another. Animal shelters will often spread the word through facebook about missing pets in a certain area. Usually that pet will be found and returned within days due to the local community keeping extra watch.
I have no plan to register a Facebook or Twitter account. The disadvantages still outweigh the positives for me. I don't want to take the time to manage my feed so it only shows relevant results that aren't "dur hur meme, I had chilled beans last night and check out this duck face i took while riding the rollar coaster, p.s i was sick all over me bf at the end lol".