...the code being accessed w/o my consent? I remember reading that .swf files can be easily decompiled. What can I do to prevent that from happening to any .swf files I produce?
It's just a weakness in the swf platform, in future versions of flash it may become harder but there's nothing you can do really.. there are products like this http://www.kindisoft.com/secureSWF/actionscript-obfuscator.php
but it will take someone who knows what they're doing just an extra hour or so to work through.