Plain Flash SWFs are trivial to decompile and decompilers have been available basically since the beginning of the platform. Anyone who really worries about that sort of thing is running their Flash output through obfuscators/minifiers similar to the ones available for JavaScript. With such obfuscated swfs you can still extract the code but it'll be basically an unmaintainable mess. I'm sure the output of such obfuscated code with this tool is just as bad as it would be if decompiling the bytecode to ActionScript, if not worse.