I think it is. I rarely use this option, preferring to create unique accounts for each service. I suppose most people will just use their Facebook account wherever they can and possibly think all those services are "Facebook" somehow.
There is a trade-off between security and convenience and people are known to choose the path of least resistance. So unfortunately, online security is not great at this time.
There is a trade-off between security and convenience and people are known to choose the path of least resistance. So unfortunately, online security is not great at this time.