I recommend reading Jerry’s Comment and my reply, which focus on whether the definition of “weblog” is the crux of the problem. I think the issue is whether the term “weblog” is being used in a misleading way: “To my mind, lexBlog, for example, is offering to create and maintain websites that utilize the very easy-to-use and flexible ‘weblog technology.’ But, if it is going to call the resulting website a weblog, it needs to make clear to lawyers buying the service that their results may differ greatly from the personal, traditional weblog, and let the visitor to the site know clearly and unambiguously when the purported owner-editor is not the actual producer of the content.”

The first question is particularly easy: It is not necessarily unethical for lawyers to use materials written by third parties in their marketing efforts. Paper versions of such materials have been around for many years from a variety of vendors, including the American Bar Association. If lawyers can use such material in the form of paper newsletters, then there is no apparent reason why they can’t be used on blogs.
Here is the Comment that I left on Jerry’s website, in full:
I’m always a little surprised to find out that an ethical question I’ve raised is “particularly easy to answer.” You’ve made it so easy, I guess, by slightly changing the issue to a bland, general question “Is it unethical for lawyers to use marketing material written by third parties on blogs?”
Your wording leaves out a final clause that goes to the core of the ethical problem — something like “without acknowledging that the weblog editor/owner did not find, choose, summarize, analyze, provide the commentary, or otherwise create the content presented on the site.” I think the issue of acknowledging the source of the content poses a far more difficult question (at least if you’re trying to justify the practice).
For example, the YourLaw newsletter for clients that you have linked to at the ABA website clearly indicates that the AMA is the source, and the sample picture of an “imprinted” edition states — right under the masthead and easy to see — that the newsletter is “compliments of” the law firm sending the material.
You don’t seem to have answered question 2 or 3 at all (by, for example, showing a connection between the ability of weblogs to permit easy communication and the way prospective clients actually choose a lawyer), so I look forward to the further thoughts you have promised.
As usual, we hope you’ll straighten us out!