I've blocked a few opinionated, obnoxious people from facebook in the past. I've also deleted several people that I haven't made contact with for years. But I've been deleted or blocked in the past from colleagues at work. Half the time, it's not them that I've upset, but another colleague. After the initial surprise, I find it quite amusing. Especially when the 'blockee' tries to contact me on facebook later on for time off etc and has to send it through private message where it shows that we are not 'friends'.
I don't usually take it to heart, even from people I know quite well. They have their reasons, I respect that. I honestly wouldn't worry about what people that I don't know think of me. Striking up a conversation with one person online, you need to have a common bond as there are no physical attractions or body language to respond to. If you are on the telephone and want an escape, you can say 'i'll call you later, there's someone at the door/dog needs a wee/food burning in the oven' etc. Online, there is no need for such niceties, some people just stop the conversation dead, as there is less emotion in typing than talking.