While this might cause some confusion regarding expectations--that's a big part of learning to write. So in a way, by providing them assignments with very different purposes, audiences, and/or expectations you are preparing them for real-life academic writing experiences where one professor might assign--oh, I don't know--a blog writing assignment and then a book review. They need to understandt that what is acceptable in one context is not necessarily going to fly in another.
Certainly--the assignments in English 110 are apparently designed to prepare students to have to write completely different kinds of papers--textual analysis vs. position paper vs. research paper--making sure the students can see the different purposes of the assignments. Despite different purposes, those are all academic (transactional) writing--and although blogging is less formal (more expressive), it doesn't usually go towards the literary (poetic).
My assumption was that "poetic" writing is generally reserved for creative writing classes--not exactly what 110 is designed to prepare students for. So I want to teach my students different modes, but I wonder if those should be mostly of the transactional sort. I should admit, however, that I recall doing four creative writing projects in my college career, and I didn't take any creative writing classes (Feminist Theory, Global Futures, Prose Fiction, and Senior Seminar). We don't see much creative writing in the writing center, either, but I think that has partly to do with students being less comfortable getting help on "creative" assignments.
It seemed to me, at least when I wrote the last post, that the memoir is easy to teach in such a way that makes it a different kind of writing than anything else they'll have to do--variety is good and all, but I don't teach my students how to write sermons or screenplays because my job is to prepare them for "academic writing." I do think, however, that the memoir can be taught as a more "transactional" piece, but that it may take some effort to do so. I guess I'm still not sure how important that effort might be.