"The work of creating the site is ongoing, and the features it will include are being introduced gradually in a series of new site releases. One of those releases, with some new features, will go live early next week. However, media reports that have appeared in the past day or so have given the impression that all of the features we’re planning are ready to be released, but that's not the case," the note reads.

While Encyclopaedia Britannica is a venerable, centuries-old print institution struggling to adapt to the Internet, Wikipedia is emblematic of the Web's power of disruption. Written and edited by thousands of volunteers worldwide, Wikipedia publishes edits and contributions immediately without an approval process for most of its entries. It relies on the "wisdom of the crowd" for its accuracy, although that accuracy has sometimes been questioned.

Another big difference: Unlike Wikipedia, which is free, Britannica.com requires a paid subscription to access most of its content, which affects its popularity and visibility to search engines, something Hitwise brought up in its note.

"One of the big questions still on the table is whether Britannica will open its content or maintain its premium membership paid wall. In order to compete with Wikipedia in the Google [search results], Britannica needs to build up inbound links. If content is locked up behind the paid content walls, people will be much more likely to link to other websites with free content -- such as that available on Wikipedia," wrote Hitwise analyst Heather Hopkins.

As of last week, Wikipedia was the 13th-most-visited site on the Web overall, while Britannica.com ranked 2,349th, according to Hitwise. People who visited Wikipedia spent an average of 10 minutes on the site for each visit, compared to a little under three minutes on Britannica.com, Hitwise said.