This free, collaborative, Web-based encyclopedia has been making waves lately for its popularity and its controversy. Wikipedia, which at the time of this writing boasted 558,253 encyclopedia entries, has just become the second-most visited reference site on the Web, according to online measurement company Hitwise (http://www.hitwise.com).

Wikipedia is now second only to Dictionary.com (http://dictionary.reference.com) and is ahead of About (http://www.about.com), Answers.com (http://www.answers.com), MSN Encarta (http://encarta.msn.com), Merriam-Webster Online (http://www.m-w.com), and Free2Professional Translation (http://www.freetranslation.com). Needless to say, all of these free services are worth checking out.

Of these sites, Wikipedia is the fastest growing by far, according to Hitwise. Its market share rocketed up a remarkable 618 percent over the past year.

But what most distinguishes Wikipedia is what makes it most controversial. Anybody can create, add to, or change its encyclopedia entries using just a Web browser. Like most Web sites, Wikipedia offers up editorless, raw content that’s free from publishing rejection.

Wikipedia, as its name indicates, is a wiki, which Webopia (http://www.webopedia.com), another free, useful Web reference service, defines this way:

A collaborative Web site comprised of the perpetual collective work of many authors. Similar to a blog in structure and logic, a wiki allows anyone to edit, delete or modify content that has been placed on the Web site using a browser interface, including the work of previous authors. In contrast, a blog, typically authored by an individual, does not allow visitors to change the original posted material, only add comments to the original content.

The first wiki, Wiki Wiki Web (http://c2.com/cgi/wiki?WikiWikiWeb), was created by Ward Cunningham in 1995 to record the history of computer programming ideas. If you type “wiki” in Google today, 44 million sites will be returned.

Started in 2001, Wikipedia is the largest and most popular wiki. Along with the English site, there also exist a staggering 195 versions in other languages. Each has its own content, and all of the sites are sponsored by the nonprofit Wikimedia Foundation. More than 40,000 people have contributed to the English version, which is the largest.

The word “wiki” is Hawaiian for “quick,” and that’s where Wikipedia excels. Minutes after the election of Pope Benedict XVI, a Wikipedia entry for him appeared.

Of course, this democratization and acceleration of information has its downside, and herein lies the controversy.

As Wikipedia’s own entry on Wikipedia indicates, no attempt is made to determine objective truth, and “because of its open nature, vandalism and inaccuracy are problems.” Wikipedia also reveals that it “has been criticized for a perceived lack of accountability and authority when compared with traditional encyclopedias, systemic biases, and deficiencies in some topics.” That sounds accurate and objective to me.

Wikipedia is “all so very Lord of the Flies,” said Karen G. Schneider in an online discussion group for writers. Schneider is a librarian and book author who runs a portal to the Internet for information professionals called Librarians’ Index to the Internet (http://lii.org).

“The ‘egalitarian’ nature of Wikipedia favors the loudest voice over the most authoritative,” she said in her personal blog (http://freerangelibrarian.com). “It reflects the views of people who have the time and interest to contribute rather than being reflective of expert opinion or even the culture at large,” she said in a phone interview.

Wikipedia has other problems as well. Though it can be extremely timely, it doesn’t always contain cutting-edge research in highly specialized fields. And because of its popularity, surfing for information on Wikipedia can sometimes be slower than on other sites.

Still, there’s charm (and often good information) to be found through Wikipedia’s populism. Just don’t forget to take it with a grain of silicon. As with the Internet in general, caveat lector, reader beware.

Information professionals recommend that you vet important information with at least two other sources when the reliability of the source directly affects the need for such fact checking. Often it comes down to how much your time is worth.

With a source such as Wikipedia, such fact checking is often mandatory. With a source written by experts and edited by professionals, the information you’ll find is typically more reliable.