Dear Miss Snark,
I often see blind ads in the backs of magazines "Manuscripts Wanted, for submission to publishers in North America" or something along those lines.
When I see an ad like that, I automatically think, "Vanity pub or scam". Am I right to assume that? Are there any legitimate agents or publishers that advertise in such a manner? Does it matter in what publication I see this (for example, is such an ad in Cosmo more likely to be a scam than one in Writer's magazine?
No legitimate agent advertises for clients. Legitimate agents WILL sometimes call you or contact you if they see your work in a publication (like Harper's, or Cosmo, or the New Yorker).
No legitimate publisher advertises for writers. They may give you guidelines for submitting work on the website but they do not PAY to solicit you or yourwork.
Reason: they don't have to. Every agent and publisher gets enough material over the transom or by trawling the net or lit pubs. Paying money to get more is just witless.
The only people who need to advertise are those who generate revenue by signing clients (ie fees for reading or publication) and not by selling books.
Legitimate publishers advertise books, not themselves.
Legitimate agents are listed in directories, not the classified ads.