Your bank probably knows a lot more about you than you think. So does your mobile phone company, but since they're separate entities, you probably don't lie awake at night worrying about George Orwell/1984 data privacy scenarios.
But what if the two entities were to merge - would you be worried about the merged company having access to too much data?
This is exactly what is quietly happening with Google and Doubleclick, which is less of a merger and more of takeover of the latter by the former.
Google probably knows a lot about your Web surfing habits, thanks to the fact that 70 per cent of Netters use its search facilities.
Doubleclick, meanwhile, also has a wealth of marketing and Internet behaviour on users, thanks to the fact that its Web marketing and analysis technology is in widespread use.
But it gets worse. Google is a very cash-rich company and almost certain to scoop up - sorry, acquire - other companies with interests in Web marketing.
If I tell you that Google's data on you is almost certainly spread across the world on multiple servers, many of which are beyond the reach of UK and EU data protection laws, would this worry you?
It worries me, which is why I've - sadly, I have to admit - stopped using Google as my search engine. (Ed: What Search Engine are you using then?)