When agents of the United States federal government began an international operation to raid MegaUpload, they were targeting after an organization that was allegedly engaged in a highly-illegal and highly-profitable piracy business.

But their actions have had a ripple effect across the internet, with other ‘file locker’ and ‘file sharing’ services questioning their own futures.

Some, like RapidShare, are fighting behind the scenes to protect their interests. But others are deciding to call it a day.

Take, for instance, BTJunkie, a popular BitTorrent search engine — the third largest of its kind according to Compete.com. A message posted on the BTJunkie website today reads:

This is the end of the line my friends. The decision does not come easy, but we’ve decided to voluntarily shut down. We’ve been fighting for years for your right to communicate, but it’s time to move on. It’s been an experience of a lifetime, we wish you all the best!

According to GigaOm’s Bobbie Johnson, BTJunkie wasn’t the target of any legal action — at least not yet. But it would appear that the takedown of MegaUpload was enough to convince BTJunkie’s operators that it was time to move on.

In light of the operation to shutter MegaUpload, numerous observers have pointed out that SOPA doesn’t appear necessary. After all, the absence of a SOPA-like law certainly didn’t prevent the authorities from going after MegaUpload, so do they really need more power than they already have?

Assuming the case against MegaUpload doesn’t crumble, the fact that similar services are deciding to close up shop certainly provides some evidence that enforcement of existing laws may be enough to thwart commercial piracy operations.

Some, of course, question whether the case against MegaUpload is proper, even though the criminal history of the service’s founder is well-established and there’s every indication that the persons involved believed they were committing crimes. But if we don’t want onerous legislation that treats every internet user as a criminal, enforcement of existing law would seem to be the best outcome.

From this perspective, while there are legitimate concerns about silencing effects, the internet community should think twice before it laments too strongly the shuttering of services whose operators clearly questioned their own legitimacy the moment they believed the law was being enforced.