This question is written "yes" or "no." While I can't say it that succinctly, let me take a shot at this. To be patentable, an idea must have 1. utility, 2. novelty, and 3. be non-obvious. If you assume that the idea has utility, then we address novelty. Novelty asks if this particular thing has ever been done before. There are new ideas every day. So, many ideas pass this bar easily. Next is non-obviousness. This is where a lot of things get hung up. You can't patent something that would be "obvious" to try or do by someone skilled in the art of the particular field.

Now, lets get to what seems to be a question dealing with public domain and the 1 year filing thing. If you have a patentable idea, you have 1 year to file from the date that you disclose the idea. Thus, if you don't file within a year of disclosure, then you are barred from filing. Why? Well, remember the idea has to be novel! If its been out there in the public for a year, then when you go to file, that idea isn't novel any longer. Your own conduct of disclosing your idea becomes a bar to your own patentability. We call that 1 year the "safe harbor" to give you a little time to get your "stuff" together.

Now, lets say you want to practice something and are afraid a third-party will claim patent rights. If its been disclosed more than a year and the inventor has not filed a patent, then the inventor will not be able to get a patent...and thus won't have anything to sue you for.

Hope that helps.