Is full post quoting tantamount to theft? The question has been asked. Naturally I think it depends, not the least bit on the sort of license under which the original material is distributed. If it's indicated “fair use” to take and quote freely then there's definately nothing illegal about it in the slightest.

But is it lazy and dangerous?

Yes and yes.

It's lazy because the quoter is just doing “”http://www.rebeccablood.net/essays/weblog_history.html">filtering" (as described by Rebecca Blood and perfected by Jorn Barger) without the link — just an oversized copy and paste. And it's dangerous because without the link (or at least without an obvious link, few sites take material entirely without citation even if that citation is difficult to find) the connection between the original material (where a very interesting conversation could be occuring) and the posted copy might be lost.

Is it wrong to quote full posts? Well, that's for everyone to decide for themselves. I say if you like something, link to it. Start a “remaindered” (or “link”) blog if you don't want to write commentary. But if you want to discuss something, quote from it. Not all of it.