Here are the three most significant problems from my perspective: (1) Cost - IP allocation isn't close to free, either in $ or in time/administrative overhead.

Here are the three most significant problems from my perspective: (1) Cost - IP allocation isn't close to free, either in $ or in time/administrative overhead. (2) Technical Complexity - Using routing protocols like BGP is not currently a process with enough automated tooling to make it realistic Those problems could likely be overcome with concerted effort. But the biggest problem of all may be what this would do to the size of global routing tables. We've already got a problem with routing table size exploding with more and more people advertising smaller and smaller prefixes. All of that high-performance ram is expensive. That routing table is globally replicated. If it were affordable for everyone to announce their own prefixes, routing tables would be prohibitively large. I don't think we yet have any good answers to this problem, and I am genuinely interested if you are aware of any.