Pete, that's a standard policy of the typical website and it sounds like a cop-out. What you describe is the absolute minimum for which you are responsible. I can appreciate that a mostly volunteer organization cannot be expected to run down every possible lead, however there are a few compromises that I would like for you to consider.
First, do something proactive to let your participants know that it is technically illegal to replicate a substantial portion of an authors article on this site without permission. Policies should encourage posting of links and summarization of facts rather than cut-and-paste. This should be a key point just like the no-posting-of-names in the Special Rules thread.
Second, this happens with such frequency that there are plenty of obvious violations which would require almost no research before converting the reproduction of an article into a link. See, for example, the first two posts of this thread. The first post, by attribution, was a work clearly written by someone other than the poster. The second post represented someone posting the link back to the original. The OP should have set it up that way in the first place, and ScubaBoard should promote and require that in an attempt to be a good internet neighbor. However, when someone posts like this, it's really a no-brainer for a mod to snip it down as was done for this thread. Doubts should be resolved in favor of the content owner if there aren't enough resources for research.
Third, a little goes a long way. The general policy and attitude here is one of entitlement with regard to these issues. There is very little respect for the rights of authors who aren't posting here. A few changes to policy and practice could change the culture in a positive way. Clearly, it is important to many of us here to understand and learn from things that happen in the diving community, both good and bad. We can do that just as well with summaries and links as with complete replications of the work of others. If there is a little education and a little enforcement, maybe people will start to do things the "right" way.
Fourth, ScubaBoard should be interested in self-preservation. While it is accepted a host isn't directly responsible for what a visitor posts on their site as long as they remove it upon request, the laws are still evolving. I wouldn't have to stretch much to see an attorney make a case that ScubaBoard's policies promote the theft of copyright and that they should therefore be liable in some fashion for the violations. It would take little effort to locate dozens of cut and paste replications of accident reports and related articles among other things to show such a pattern.
With regard to "fair use", there are a number of characteristics that are examined to decide a case. The standard set are as follows:
1. The nature and purpose of use of copyrighted work. For example, is there an intent to profit from the reproduction. The only direct profit made from these is in the form of ScubaBoard's increased traffic and advertising revenues, but that is largely discounted. There is also leeway when the use is for educational purposes, and one could argue that this is often the case here. Personally, I would argue that the educational intent could be served equally well by summary and link without the copyright violation.
2. The nature of the original work. In this case, it would not be obvious that the author had the intent for the work to be copied all over the internet. In fact, the copyright statement at the bottom of the page would suggest just the opposite. As I read the original, I get the impression that it exists as a sort of advertisement for the services offered by the author's firm. That is an end which is not well served when the entire article is replicated on another site, especially without a link back to the original.
3. The substantiality of the use. This is an examination of the percentage of the original work that has been replicated. While there is no overall rule about the number of lines that may be reproduced, the larger the percentage of the whole that is taken, the less likely it is to be considered a "fair use". My reference to a "line or two" in a previous post was based upon my perception of a balance between what would be necessary to convey some meaning versus what would be a substantial reproduction. It is much harder to argue "fair use" when the entire work is replicated as in this case.
4. The impact of the replication. If the original work was created as a means to draw eyes in to the owner's site, then a full replication obviates the need for anyone to go there. That owner's site loses the traffic and potential income from any of their own advertising as those eyes go to another location, like ScubaBoard.
This particular article is reported as intended for replication by the author. That doesn't make it any less valuable to discuss, and hopefully rectify, ScubaBoard's position with respect to the protection of copyright. The penalties for copyright violation can be severe, but more than that, it's unethical.