A University of California, Berkeley study found that Web users may be tracked by dozens of sources on a visit to a single site. Within a single month, the researchers found 100 monitoring agents on the site blogspot.com. Although many of the trackers used on blogging sites are low-level monitors used by bloggers to see who is reading their posts, major companies also are tracking a significant amount of Web traffic, according to the report.
The researchers note that many large companies have hundreds or even thousands of affiliates, sometimes in completely different industries, and occasionally in foreign countries. Please refer here to read this interesting research and report on DarkReading.