The company has already had to put in a little more work. In addition to all of those members, the network was also hit by spam early on, with fake accounts for people like Steve Jobs and Jonathan Ive, plus links that led off to contact-stealing scripts and other trouble like that. Apple has already cracked down on most of the offenders, but clearly it was an issue early on that they didn't foresee.
The interface has already been updated a bit -- Apple has added "back" and "forward" buttons to the service, to match the rest of the in-app browsers in iTunes. I still maintain that Ping won't reach its full potential until you can actually "like" songs and albums in your personal library, so hopefully a few more updates and tweaks are on the way.