Things that should not be vacuum sealed
I'll update this post as I find things that just don't vacuum seal well.
Broccoli and Cauliflower. When stored in a low-oxygen environment, these vegetables produce the most horrifying of odors. It's not so bad if they've been blanched, but raw is definitely a problem. Avoid at all costs.
Scallions (in bags). They get squished, and then they appear to go bad faster than they would in a normal loose bag.
Lettuce (in bags). Lettuce in jars is great. Lettuce in bags gets crushed, then seems to spoil fairly quickly. I suspect that the act of squishing is bad, which is not surprising because it presumably breaks the cell wall of the plant.
Radishes vacuum sealed for long periods of time (weeks) appears to not work as well as you'd think for a relatively sturdy vegetable. The bag appears to inflate somewhat, the color leaches out, and they get very wet. Something is going on chemically but I don't know what yet.