Opiniatrety

Nichols, Stich, and Weinberg (Weinberg et al 2001, Nichols et al 2003) have argued ....?

According to the Chicago Manual of Style, 15th edition, an author-date citation "denotes a work, not a person" (116.115). The citation is "usually placed just before a mark of punctuation" (116.112). Your sentences suggest that the works have argued such-and-such. If you want to say that the authors have argued such-and-such, it seems that you would have to say the following:

"DeRose has argued that ... (1998, 2002)."

"Weinberg, Nichols, and Stich have argued that ... (2001; Nichols, Stich, and Weinberg 2003)."

If I were writing such a passage, I would drop in \cite tags and have BibTeX construct references.

You should do whatever you you feel inclined to do. If the paper in question is accepted somewhere, it will be transformed into house style regardless. Since journal house styles vary widely, spending much energy on it now will buy you nothing in the long run.

Note that if you follow CMS' conception (a work, not a person), you ought to use present tense: "WNS (2001) and NSW (2003) argue that..."
And note that this would lead you to "Weiner (2003, 2004) argue that..."--but you'd probably go with "Weiner (2003,2004) argues that..."

I've usually figured that "DeRose (1998)..." denotes the person DeRose, citing his 1998 paper, whereas "(DeRose 1998)" denotes the paper itself. This leads to oddities such as "In the first section of (DeRose 1998)..." but "In the first section of DeRose (1998)" is no less odd. I think I've seen some journal explicitly advocate this practice, but it's obviously not Chicago Manual. P.D. is right, too, and I think Richard may have the most elegant actual solution. (How's that for trying to please everyone?)

Let me take this opportunity to direct everyone's attention to the previous massive philosophical post. Actually I shouldn't be surprised that a concise post that acts an actual question draws the comments.

Oh, and there's a rather stupid typo in the first paragraph of the main post. I think I'm going to leave it up, since the sentence is most likely true as it stands.

In the CMS, anyway, it appears that the parentheses are used simply to indicate parenthetical remarks, not to distinguish between authors and works. "A locution such as 'in Smith 1999,' though technically proper, is awkward and best avoided. Reword--for example, 'Smith's study (1999) indicates that..." (16.115)

The CMS does give one example that I'm not sure about. "Where the author's name appears in the text, it need not be repeated in the parenthetical citation. 'Litman (1983) finds that Academy Award nominations or winnings are significantly related to revenues.' " (16.112)

I'm inclined to think now that "Litman" denotes the author rather than the work. So maybe your original DeRose sentences is ok. Then you could say the following:

"Weinberg, Nichols, and Stich (2001; Nichols, Stich, and Weinberg 2003) have argued that..."

As for Richard's suggestions, the CMS is clear that all of the names should be included for works by two or three authors. (16.118)

By the way, I'm certainly not saying that you must follow the CMS. I just happen to own it and have it on my desk.

CMS also has the advantage that, if someone queries you about how you format your citation, "Chicago Manual" sounds better than my preferred alternative, "I pulled it out of my, um, ear."

I think the second and third paragraphs of your post are pretty much what I was thinking of; the majority of my citations wind up being like that.

Apropos of nothing: Why are citations for books supposed to cite the city of publication first and then the publisher? Maybe back in the day you had to travel to London to find the book but now that just seems silly.

I'm not sure why book citations need that information at all. Hardly anyone goes directly to the publisher to find books anymore. There seems to be an inconsistency in the requirements, too, because the publisher and city are not given for journals.

I say we start a petition right here to change the standards. It would make life easier to just get rid of that information in citations, because often there are multiple publishers and cities listed at the begining of books, so it's not clear what should be used.