Key to Google's defence in the Viacom v YouTube case, should the MTV owner's copyright infringement lawsuit against the video site ever actually get to court, will be that the search firm and its video sharing offshoot religiously respond to all and any take-down notices issued to it by US content owners under the take-down provisions of America's Digital Millennium Copyright Act.

Proactively responding to such notices, they shall argue, absolves them of any liability for any copyright infringing activity their users might undertake, even if infringing content is available via a Google-powered website for a short time before the take-down notice is issued and actioned.

And it's true, Google are among the most proactive when it comes to actioning legitimate take-down notices - something that has started to cause some tricky PR dilemmas for the web firm of late with regards Blogger, the Google-owned blogging platform. Especially now, as a number of prolific music bloggers are accusing Google of turning off their blogs overnight, with no warning, on copyright grounds.

It seems Blogger updated its terms and conditions regarding DMCA take-down notices, relating to blogs it hosts, last summer, which has resulted in the Google blog platform becoming more rigorous in its response to such notices. The service says that normally it will set a blog post containing allegedly infringing content (most likely a link to an unlicensed MP3 or video file) to 'draft status' so it is not publicly accessible, and then send an email to the blogger alerting them to the infringement claim. The blogger can then either appeal the take-down notice or remove the post.

However, where multiple take-down notices are issued against one blog, and the blogger doesn't seem to be appropriately responding to email alerts about infringement, Google retain the right to shut that blog down. It seems that six months on from the new rules being introduced, the shut downs have now begun, which is why there is suddenly so much chatter about Blogger and DMCA take-down notices this week.

Among the US music blogs to have been affected so far are Pop Tarts Suck Toasted, Living Ears, It's A Rap, Masalacism, To Die By Your Side and I Rock Cleveland. Despite Blogger saying bloggers targeted by take-downs can appeal the copyright notices, I Rock Cleveland's Bill Lipold says his efforts to convince the Google platform that his posting of MP3s to his blog was totally legit and artist-endorsed were unsuccessful.

He told Cleveland newspaper The Plain Dealer: "It's difficult to get across ... that there's a difference between someone working with the blessings of the artists and the labels and someone who leaks Bruce Springsteen's entire discography. They don't see the distinction between someone who's adding value and someone who's facilitating piracy. That goes to the root of this whole mess".

Of course, it is tricky for Google. As a multi-billion dollar enterprise they are entirely worth suing if any content owner genuinely thought they were failing to fulfil their obligations under the DMCA.

And you can sort of see why they wouldn't want to be anything other than the delivery boy when it comes to DMCA take-down notices, given that it's not entirely unknown for one part of record company to ask a blogger to plug an artist by posting an MP3 on their site, and then for another part of the same record company to cry "copyright infringement". And that's before you even consider the grey area with regards publishing royalties when record labels give away MP3s via blogs and other media as a promotional tool. Google would much rather Lipold dispute take-down notices issued against him through the formal channels rather than having to mediate in a "but what about the promotional value" debate.

There was some chatter to the effect that when Blogger blogs like those mentioned above were shut down, a blog's owner lost access to his or her own content - ie their own intellectual property - though it seems it is possible for affected bloggers to reclaim their own work, though whether comments and the like are included, I don't know. Certainly at least one of the shut down blogs has managed to resurrect their site on another server, and it looks likely the others will follow suit.

Which is, of course, what will be the actual result of Google being responsible copyright citizens - any bloggers posting MP3s, even those doing so entirely legitimately, will quickly sign up to rival blogging platforms, or set up blogs on their own servers using Wordpress or similar blogging technology.

I've no idea how it would work, but I suspect everyone could benefit from some sort of record industry-led system whereby legitimate bloggers - especially those blogging entirely without financial reward - could get some sort of certificate that says this is a blogger who only posts MP3s where permission has been specifically granted, and therefore deserves the benefit of the doubt when take-down notices arrive.