The Click problem occurs only during Video Recording with sound enabled. It will only happen when you pan the camera in any direction quickly. If you hold the NEX-5N closely to your ear and move it about slightly, you will also hear a clicking sound. This is what is causing it. The stereo mic is picking up this sound from the internals. People on the net speculate that is the orientation sensor (ball bearing contacts). Strange that no one has done a teardown on the camera yet to find out exactly what is it.

But do note, if you are recording in an area where the ambient sound is noisy (roadside, markets, lots of ambient noise) you will not be able to hear the clicks, or it would be barely audible.

However, if you have already bought a NEX-5N, there will be a fix soon in Malaysia. Right now in the US, Sony is asking people to send in their cameras for a free fix. Eventually, this "fix" will be available here. If you really want a NEX-5N, pick it up, then send it back to Sony later for 7-10 days. If you're not going to do video, well, just get it! It's a great cam.

Supposedly the Click will not be found on later batches of the cameras. This is based on the news of the UK shipments; the NEX-5N shipments to UK is currently being withheld. Of course, in the end this is just a rumor.
I don't work for Sony. I just love this small little thing. 

Just shot an email over to Sony.
Hello, In reference to the ongoing camera "Click" issue for the NEX-5n:

I would like to know if any action will be taken to fix or improve the current "Click" issue during video recording with the NEX-5n. This is  quite a large problem for users wanting to record videos with the NEX-5n, with it's highly touted Full-HD abilities. At it's current state, all audio captured by the camera is rendered useless. Even with the optional external microphone (ECM-SST1) attached, the click sound is still audible, especially in areas with low ambient sound.

Sony US has acknowledged the problem and is offering this fix:

http://esupport.sony.com/US/perl/news-item...dl=NEX5Nmething

Here are a few links to several forums discussing the problem:

http://forums.dpreview.com/forums/readflat...thread=39426646

http://www.sonyalpharumors.com/sony-us-ann...issue/#comments

http://www.sonyalpharumors.com/sony-confir...ex-5n/#comments

Also, at our local Lowyat.net forums. Many users and potential buyers are concerned about this issue.

http://forum.lowyat.net/topic/1932071/+1080

Do let me know the good news.

just got a reply from SONY MY, on this "fix"

will need to wait for further instruction from Sony Regional Technical Team.

patience.

meantime, enjoy some NEX5N video samples (1080p 50p AVCHD and 1080 MP4) :

well, most important is Sony acknowledged it and offer a solution. now, you may bring your camera to any Sony Service Center.