The problem is the convenience. Remember all these Payback-, Club-, Discount-Cards, etc? The actual benefits of having one are marginal, but still lots of people use them. They only have a number on them either, but with a electronic cashing system the corporations' large databases get filled quick. The data trail I leave on the internet is bad enough (give a P.I. one week with google and he can create a psychogramm and case file of me without even having seen me), but if RL data about movement patterns, buying habits, etc is accumulated in the same way, then 1984 is indeed near.
It's a vicious circle - customers want ease of use, so they, we will agree with perceivedly small risks. As result the corporations get more data to play with and go one step further - you *need* one of these tracking mechanisms to be allowed to buy/sell/whatever. It can all be reasoned away quite nicely and within a few years it will be a commonplace.
Now one might say 'so what, there will still be only a lot of separate databases, applicable only to the field of the company using it' and indeed, if it were so the risks would be considerably smaller. But centralization and fusions abound. For example here in Germany there are two or three gigantic groups owning 90% of all chains of super markets, etc. Worried already?
Now taking this one step further, many goverments are still implementing additional 'security measures' against terrorism, which may or may not be effective. These are mostly laws to force the further centralization of databases in the name of 'pattern recognition to find terrorists'. This might indeed be the aim in some (most, for the optimists) cases, but in reality it creates a structure, that can easily be abused for much less noble aims. And what is there to use WILL be used.