I have bought content. I've also written for hire - everything for scholarly research on grant money (7 books) to dashed off blog posts to people looking for cheapish blog posts.
1 (and 2 actually). What I hate the most.
Quality. Most content I've bought has been disappointing. I've typically paid around $25-$40 per 1000 words, so not total bottom feeding, but it just never really measures up. When I look at places where I've bought some of the content and written some of it myself, my content usually wins on traffic by a huge margin and typically it's much better in terms of traffic quality too.
I also agree about images. When I'm doing the writing, I find that identifying a good image I can afford often takes me longer than the whole 1200-word article. So if I buy and article without an image, I still have a lot of time to invest in many cases.
4. Price
A big factor. At a certain point, I would just pay myself. So whereas a top-notch writer will want $50-$75 per 1000 words, in an area where I have some knowledge I can usually churn out 1000 words in under an hour and half. So if I add all the admin time I spend to tell a writer what I want, edit the copy and so forth, I find that I can't justify going over $40/1000 words (I might if I were hiring a top copywriter who might get 10x that, but I've never had the occasion/budget).
5. Quality vs Quantity
Quality
6. Elance, Writer Access, some content provider whose name escapes me. I have liked Elance. I've found journalists between jobs, book authors and a husband wife translation team - her English, him French and both highly educated. But back to #1, they were only really good for a first pass before sending the material (a book introduction in French) to my publisher. The editor in chief at the publisher still had tons of corrections, but someone like that is over $100/hour.