I think FB had just kinda been funky recently. I notice the same sort of thing, with one minor exception. I notice that my friend count does regularly go down.... but I've noticed that it also goes back up. My number is constantly fluctuating up and down without me adding anyone. Something that might contribute to this is some people might be getting hacked. I know that a few months ago, I got an email from Facebook saying that I had shut down my account. I went back, turned my account back on, changed my password, and never got the email again. So that may explain some of it.