I generally love Alex's writing and have learned a ton. This example, and one or two others, stuck out as a little flawed here. If conference sponsorships are a traction channel that proves to be successful for you relative to other channels, then more power to you. To your final point, do what works for your company. This isn't going to come from blog posts – although you may get ideas there. It's going to come from the hard work of developing hypotheses, running experiments, and using benchmarks to start the process anew.
The problem is when a startup treats a conference as a branding exercise ("we got our name out there... success!"), rather than as a means to acquire highly qualified leads so they can close deals and profit from the experience ("we got a 1000% ROI by closing $50K worth of deals... success!").