Adware is software that displays advertisements to computer users. Some of the most strict definitions of adware include applications that are sponsored for their free use. One of the most popular examples is WeatherBug, which offers a free version of weather software and comes wrapped in a skin that displays advertising.

While older versions of WeatherBug had rather significant privacy issues, newer versions are pretty straight forward: you see the ad, but you get the weather. Is this adware? In the most strict sense, many people say it is. But to some computer users, the tradeoff seems fair. Hotmail, Yahoo Mail and AOL's Instant Messenger are among other software programs and services that display ads to their users in exchange for free usage. Many of these programs off advertising-free versions for a price. Another application that is popular to users are search toolbars from companies such as Alexa. These toolbars offer desktop search convenience but also comes with Adware.

More infamous among adware watchers is Gator, which now goes by the name Claria Corp. Gator was controversial from the start. It began in 1998 offering e-wallet software. But it reports your Web surfing habits back to its parent company, which then sends you advertisements targeted according to your data.

The vast majority of people consider it a pest, especially because the software is often bundled with other, more useful software.

As for adware that reports personally identifiable information, once again tolerance varies. Some people don't want any information, such as tracking the sites you visit, revealed. Others draw the line at logging IP addresses.