According to Hitwise, Google+ received 1.79 million visits in the week ending July 23, down 3% from 1.86 million in the previous week (this data only covers the U.S.). Meanwhile the average time spent on the site by U.S. visitors also decreased 10% from five minutes and 50 seconds to five minutes and 15 seconds.
Of course it would be foolish to draw any conclusions from one month's worth of traffic on a new Web site, especially when, as noted, it launched with such fanfare, which was bound to dissipate eventually. There are also many external variables at work which could boost organic growth for Google+ in the long term, including privacy concerns at Facebook and the growing popularity of other Google products like Android and Chrome.
But one thing the inevitable post-launch slowdown at Google+ highlights is the need -- and, perhaps, inability -- of Google to continue promoting the new social platform through its other products, as aggressively as possible but also without annoying users. This is more difficult than it might seem, even when it comes to people who are already Google+ members, because of the very efficiency that is built into Google's products, which tend to be purpose-oriented.
For example, someone who is using Google's search engine may well be in the midst of some business or personal project, from which they don't want to be distracted with a detour into their Google+ account. Gmail users may be better prospects, as they can use Google+ to interact with their Gmail contacts, but only if their Gmail contacts are already on Google+. And this still leaves Google the task of somehow advertising the new social platform's utility in an unobtrusive way, that doesn't disrupt the Gmail experience.