I am curious to know why SFDC has come to be associated with Salesforce.
SFDC stands for SalesForceDotCom. The company would have retained just SF. But as trends on Social Communities started getting wider the acronym faced the uncertainty of getting hijacked by other trends.
For ex: Initially on Twitter, Salesforce used both #Salesforce and #SF as hashtags to monitor the interactions. Later, it got too crowded to use #SF since it may be SemiFinal of an event etc. So then it decided to switch to SFDC. Now this has gained the prominent Keyword status on many communities(including Stackexchange) and also on Google Rankings.