Phoneutria venom is genuinely potent by laboratory measure, and the reputation built on mouse toxicity tests is not invented. What it fails to describe is what happens to people. Large Brazilian case series report intense local pain, sometimes sweating and a raised heart rate, and little else in the overwhelming majority of bites. Antivenom is reserved for the small fraction with systemic signs, mostly children and the elderly.
One component has attracted separate attention. The peptide PhTx2-6 provokes priapism by way of nitric oxide release, an effect noted in envenomed patients and since pursued in erectile dysfunction research.
The spiders reach people because they wander rather than wait. They shelter by day in vegetation, woodpiles and occasionally banana bunches, which supplied the older name banana spider and a long tail of shipping anecdotes. Rearing with the front legs raised is a defensive display, not an approach.