This has nothing to do with personalization. I'm also skeptical it's just Google because I'm not getting traffic from Google, Bing, Yahoo or Google Adwords for long periods of time. I suspect an overall network issue or possibly another DDOS event happening somewhere. It looks like "day parting" because I always get one or two morning sales (3am to 5am) then nothing all day then, like last night BANG it all opens up again for several hours and balances the day out. My web host is also suspect and trying to contact their support used to take minutes or I could call them and get a tech on the phone 24/7, now my tickets go for days and nobody answers the phone. HG in case you're curious. I'm going to check the hosting forums to see if others are seeing the same.
Sat morning...usually banging away, sitting at zero again. The weird part is that I have paid members who are always coming & going. Looks like a network issue.