The same argument could be applied to the persistent problem of pirated software, music and movies. Should we stop making these things, or hold back on development, because a handful of dishonest people steal things?
I have been designing websites for 10 years and I have yet to reverse engineer a flash file. Most design firms would fire an employee for doing this. The possible legal problems created by ripping off things from another website are too great. Even if some hacker-type decompiled the flash file, the task of customizing the animation and changing all the tweening would make it a daunting task at best. No legitimate designer/firm would bother doing this.
If there was a virtually invisible watermarking feature built into the export it would help with intellectual property rights.