I've got a shared hosting service where I run WordPress for a blog. As such I have no direct control over the web server, nor what my hosting provider might decide to record of information, nor do I have time to audit what WordPress changes for each update.
Since I'm a programmer by trade, and my blog deals with programming, it's reasonable to assume someone might consider my blog "professional or commercial activity". Maybe I'm saved by some hard criteria defining "professional or commercial activity", but to be frank, it's not worth my time going through the entire GDPR to find that out.
As such I'm not going to take the risk of being in violation and will be shutting down my blog. Instead I'll likely be reverting to posting on Google+ or Facebook, if I bother posting more at all.