Seems also to be a matter of circumstance. A person investing all of their assets into solely gold or solely bitcoin seems to be speculating to some degree. The dude with the bitcoin is more likely to lose his shirt, but may very we'll come out ahead, if bitcoin doesn't tank. Maybe placing a small percentage of assets in bitcoin could be considered an investment?
Probably more so than the roulette table. This article is weird. The author seems to miss the point that bitcoin isn't simply a digital currency without any other characteristics. The digital currency BTC is a facet of the bitcoin network. Buying BTC is more like investing in the Euro. A Euro will always be a Euro, but the number of Big Macs that a Euro can buy might increase if the Eurozone is doing well and there is an increase in the demand for Euro's.