Samples of web 2.0 logos here.
To educate my clients and blog readers, web 2.0 logos from those examples on the link (above) are mainly for website use. Whenever i heard web2.0, i think of; Gradient, 3D, Translucent, Shadow Effect, Trendy, sometimes Minimalist and sometimes colorful. Those are keywords that recognize the web2.0 logo style based on my experience and exposure to the world wide web.
According to wikipedia: [read the complete definition here]
Web 2.0, a phrase coined by O'Reilly Media in 2003 and popularized by the first Web 2.0 conference in 2004, refers to a perceived second generation of web-based communities and hosted services — such as social-networking sites, wikis and folksonomies — which facilitate collaboration and sharing between users. O'Reilly Media titled a series of conferences around the phrase, and it has since become widely adopted .
Although the term suggests a new version of the World Wide Web, it does not refer to an update to Web technical specifications, but to changes in the ways systems developers have used the web platform. According to Tim O'Reilly, "Web 2.0 is the business revolution in the computer industry caused by the move to the internet as platform, and an attempt to understand the rules for success on that new platform."Some technology experts, notably Tim Berners-Lee, have questioned whether one can use the term in a meaningful way, since many of the technology components of "Web 2.0" have existed since the beginnings of the internet.