Google+ got a ton of buzz when it launched in June, and got a lot of visitors thanks to its integration across Google Web sites.

But people don't seem to be sticking around very long after they check it out.

Earlier today, social marketing company DreamGrow posted some stats from Alexa that show a steep drop-off in Google+ traffic as a percentage of overall Google traffic.

At the beginning of August, 2.89% of all Google.com traffic coming into Alexa's tracking system was coming from Google+. Now, it's only 1.84%. That's a drop of nearly one-third in less than a month.

Alexa is not the most reliable way to track Web traffic, but numerous reports from Experian Hitwise show a similar pattern: lots of people are checking Google+ out, but they seem to be dropping out pretty fast.

Anecdotally, it seems like the site is pretty active -- we're still getting dozens of notifications about new followers every day, and there are some interesting posts and debates showing up there. It's definitely not a dead zone.

Plus, Google still has a lot of tricks up its sleeve -- in particular, letting businesses set up their own Google+ pages could help spur adoption.

But there's a big jump between early adopters and mainstream users. So far, most normal people don't understand why they need Google+ -- if they've heard of it at all.

Remember: Google Buzz started off hot, too.

See also: These 19 Social Networks Are Bigger Than Google+.