Lots of things become easy to replicate after they've been done once, despite being non-obvious before. The "no obvious inventions" part of patent law is supposed to prevent people from patenting things that are already broadly used (or small variations on things that are already broadly used). The cliched example being that you can't patent the wheel.
Edit: I see that Animats has covered this much better elsewhere in the thread.
> Lots of things become easy to replicate after they've been done once, despite being non-obvious before
Maybe, but this is not why we have patents.
Patents justification is to help innovations to spread, by making them public and, in exchange, granting a monopoly for some time as would have been the case should the innovation been kept secret.
Patents are not, in theory, a bonus for whoever implement something first.
In practice though, this seems to be largely the case, at least in software, that patents are like those mine field maps during the gold rushes, partitioning the hills and delimiting every tiny area belonging to one miner, probably to police what would otherwise be a violent, perpetual quarrel.
