Technology to help or replace primary researchers?

Wal-Mart are looking to take shopper observation to the next level. They intend to deploy infra-red based technology [1] for tracking shoppers' progress through their stores. Previously this was the preserve of observers with clipboards as described in Paco Underhill's Why We Buy [2].

Technology can help primary researchers gather much more raw data much more efficiently, but is this going too far?