Apologies first for being slow to get back to this thread (I've been tinkering in darker corners of the site [and talking nonsense on Twitter, a bit]); and also for bumping the damn thing!
Anyway, just IRT to the on-topic toward the top...
The sections in our Rules/T&Cs would, we hope, make our position on liability clear. We'd also like to think that it's obvious to anyone with even the meanest intellect that a noticeboard can't be held responsible for what someone pins on it, and similarly the person posting to a forum is accountable for the content they post.
However, we live in a world of ambulance chasing solicitors chasing the insurance companies of banks [as an aside, my tip is to wait for the motherload - I'm sure we'll have ads about claims for 'misinterpretation of the exclusions in the data protection act which lead to endless pestering by pop-up solicitors' on our screens soon]; and that complicates things somewhat.
Looking at the two scenarios discussed here..
Firstly, the issue of modifications etc. which will invalidate your insurance if not declared, or perhaps even your MOT regardles, discussed here which members may perform to their cars. The crucial point here is that as far as using a vehicle on the road goes, there are very clear lines of responsibility for the owner/insurer/driver of a vehicle. Upon traffic police finding stopping any vehicle in contravention of road traffic laws, the driver is primarily held responsible, because it's made abundantly clear that the driver is responsible in ensuring the vehicle they take on the road is safe and legal with which to do so. If the driver is not the owner/policy holder, they may also face repercussions under certain circumstances.
Insurers views are also pretty clear: If your policy doesn't allow modifications, or you haven't declared them, you're likely to void it; meaning that potentially (and in the vast majority of cases) they won't pay out on any claim - regardless of whether or not the claim is a result of whatever change voided the policy or not.
In short, "I saw it on a website" does not wash with the police/insurers.
Now, getting back to big business and ambulance chasers... Civil cases by definition don't have the same clear boundaries (this is arguably what makes them civil rather than crown cases). Again, we'd hope, that our putting ASN's position on liability for post content in writing, coupled with the common sense normally found in anything brighter than a potato would mean that we'd not be dragged over the coals for something numptyish posted by a numpty; however, that doesn't in all cases mean that big business and artful counsel wouldn't have us in the dock to test how well our T&Cs/Rules stand up to barrage by money and jargon. In that case, whether it does or not is completely academic, for two reasons: fighting the first case would most likely bankrupt us, and again whether it did or not, the site would likely be pulled because we certainly couldn't risk fighting a second time.
So, we have to be aware of both the differentiation between criminal (or road traffic) law and civil suit, and balance that with what the site is actually here to do.
All the best,
Rob.