No, this is a common misunderstanding of the implications of first to file.
Publication or public practice of their work is prior art. It immediately precludes third parties from patenting their work. (And, after a grace period will preclude them as well)
First to file deals with interferences, when two parties try to patent the same work at the same time-- it doesn't change how prior art works.
Of course, it is still useful to file defensively since relevant prior art is much more likely to be discovered when it exists as a patent... if it's not discovered a patent could be incorrectly issued. (The patent would be invalid-- but could still be used to harass people until put out of its misery by a court. :) )
Publication or public practice of their work is prior art. It immediately precludes third parties from patenting their work. (And, after a grace period will preclude them as well)
First to file deals with interferences, when two parties try to patent the same work at the same time-- it doesn't change how prior art works.
Of course, it is still useful to file defensively since relevant prior art is much more likely to be discovered when it exists as a patent... if it's not discovered a patent could be incorrectly issued. (The patent would be invalid-- but could still be used to harass people until put out of its misery by a court. :) )