AlertSite has been tracking the social network sites since last December, and says it has found consistently similar response times for each site throughout.

FORBES: MySpace's Response Time Slowest Among Social Networks

Google has previously said the large-scale tracking involving its advertising network was inadvertent.

WSJ: Google to Pay $22.5 Million in FTC Privacy Settlement

It now averages more than 270 million monthly users, according to AppData, a tracking service from research firm Inside Network.

WSJ: HEARD ON THE STREET: Zynga Wants to Be More Than Just a Facebook Friend

That network is effective in tracking fugitives down.

FORBES: Rengen Rajaratnam Rides Shotgun With FBI Back To U.S.

The big idea: putting sensors everywhere that communicate in a mesh network and allow real-time tracking and optimization of everything from traffic to the power grid to the water supply.

FORBES: Researcher Throws A Wrench In IBM And HP's Sensor Networks

This year, the network has more than 2, 000 people tracking variations among 600 species of plants and animals in the U.S., Canada and Mexico.

WSJ: A Science of Signs of Spring

Tracker Network says it has sold 130, 000 tracking devices in Britain.

ECONOMIST: Car theft

The national network will help health authorities spot disease outbreaks by tracking doctors' reports, admissions to hospital casualty depatments and sales of medication.

BBC: Early warning system for bio-terror

The group relies on a network of Syria-based activists that have been tracking the number of dead, injured and missing since the Syrian conflict began in March 2011.

NPR: Syrian Regime Battles Rebels Outside Damascus

By placing a tracking cookie on a user's computer, an advertising network can collect information about the user's web-browsing activities and use that information to serve online ads targeted to the user's interests or for other purposes.

ENGADGET: Google to pay $22.5 million to settle FTC charges over tracking cookies in Apple's Safari browser