The rule about reciprocal links relates to links between blogs or websites.
Google uses a variety of measures to assess the value of a Hub, blog or website. One major criteria is the number of people who link TO it (a backlink). Their algorithm sees every backlink as a 'vote' in favour of your Hub, which worked in the early days of the internet - but over time, website owners started to find ways to artificially inflate their backlinks.
Google isn't stupid, so it's always trying to tighten the algorithm so it doesn't count fake backlinks. One widespread trick was for two webmasters to say, "you backlink to me, I'll backlink to you" - so nowadays, Google immediately assumes that's suspicious, and discounts the value of the links.
Linking between your Hubs, with your Twitter account, and on Facebook is different because Google will probably recognize they all belong to you anyway.