Several years ago, in my 20's years it was my priciple to trust everyone (especially in peoples) until won't prove otherwise. This was functional some years, but I finally had to admit it that is not a very good "strategy", because I was disappointed many times (sometimes by peoples in whom I believed the most). After this period, I changed my philosophy, and started to use your strategy (false until the opposite is proven), but using this "model" I missed a lot of opportunities in my life (between which the Bitcoin in extremely early phase - 2010-2011). And finally...some years ago I started to "mix" these 2 visions, looking carefully between possibilities / informations. I can tell you, it is much more OK my life than before (of course, it is just my personal opinion and experience).

I think the essence is to be attentive and very careful.