Yes and also certain events like Mt. Gox will always cause a spike in activity posts here, so I thnik you can not just make a blanket statement that pure volume on these forums indicates interest.
I think the article makes some good points, but in general misses the forest for the trees. I like what I see lately with nasdaq, WSJ, and some other giants talking about bitcoins with positive spins. To me this is the most important indicator. Then soon after cryptos seep from the geek world to the regular world, it will grow. I really do think that cryptos are the future, and there is not any point to worry about them going away.
Well I'm sure that quite a portion of the users don't even know how to view the
statistics of this forum. At least I've seen a number of people asking about it.
Spikes like the one regarding Mt. Gox will never show the true situation. There was a high influx of users/posts which we can clearly see. March 2014 had the most amount of registered users in a month.
I guess there is no way to really tell the exact or even approximate (with an acceptable error margin) number of people that are using Bitcoin.