Weighing in at two thirds less than aluminium, magnesium is the lightest structural metal.

A bit like titanium which many think is some wonder material but in reality the engineering benefits are less than one would hope for due to it´s weakness.

Hua? Titanium alloys are very strong. Far stronger than 7075 AL. Grade 5 titanium has a UTS of around 138,000 PSI which is about as strong as a grade 7 medium-carbon-steel bolt.

Yup, there are good reasons why out of all the climbing gear companies in the world nobody makes any Ti gear, it´s been tried for cams, karabiners pitons, ice screws, nuts etc and never worked. The expense of the material isn´t generally of any concern since most gear uses so little but loads of other factors make it a poor choice, where Ti does have advantages over other metals is in areas generally of no interest to climbers except for bolts where the weight is irrelevant and the weakness and price of the material is a considerable problem.
The most common application for Ti in the outdoor industry is probably cooking gear which probably says more about the power of advertising than any real benefits since my cheapo aluminium pans work better than my Ti ones.

Magnesium is similarly let down by it´s weakness and considerable difficulties in working and the future at least in the short term is probably aluminium composite forgings which seem to display most of the desirable features we need for much of our gear.

Sure, I agree that titanium is not all that worthwhile in the climbing realm. But titanium does have one application in which it greatly excels. That is applications in which strength and weight are important, but corrosion-resistance is also very important. Most titanium alloys significantly outperform austenitic and even superaustenitic or duplex steels in terms of corrosion performance, but still retain a reasonable amount of strength and lightness. Titanium also seems to be one of the best if not the single best option for surgical implants due to biocompatability, low weight and high strength, and high corrosion resistance, as well as the fact that you can go in an MRI with a Ti pin but you cant use one with a 316L pin. But I agree, the Ti name is overinflated and the material is not too necessary that often.

I'm dubious about your claims of titanium's superiority for surgical implants. As I had it explained to me, the primary considerations are brittleness and removability. Since steel is considerably less brittle it is the best choice for use in applications that are subjected to high strain. That was the rationale stated by my orthopedist for choosing steel for the two plates and a dozen screws in my ankle and foot. The other aspect is removability. Since Ti rapidly oxidizes with exposure to air, creating a microscopically textured surface (but does not corrode in the body) it encourages bone to attach to it, making it unsuitable for applications in which a piece may be removed. Since one big screw holding my ankle together while the joint healed was to be taken out later, again they chose steel because it's smooth surface does not encourage bone to to attach as readily as titanium.

Speaking of the future of gear, what about the "strong aluminium alloy, special hardening treatment" of the 19G Edelrid karabiner ?
http://www.edelrid.de/en/sports/products/hardware/nineteen-g.html
Is it a revolution or an engineering/marketing trick?