It's ridiculous to measure the popularity of any non-Facebook service by number of Facebook fans. The percentage of users who fan a page of Facebook can vary vastly between competing companies.
I wouldnt say totally preposterous to compare. After all these companies rely heavily on Facebook for their marketing, of course their email list is probably their key marketing tool, but that info isn't available. Then again, I did also write the article so I am a little biased, thanks for the feedback.