I'm with D4...
I have put two of my betta in those small quart sized betta hexes...a temporary situation as I had to use the 10 divided I had them in to house some juvenile rams...well...
I used Echo-Complete as the substrate and added some small live plants....and those betta have been doing just fine in these tanks. Algae, not a problem...plants doing very well (I dose with excel)....betta...seems happy and healthy and haven't had an issue with either of them since being in there. And frankly...I don't change the water every day either...about once a week. I believe the plants are a big help here.
I keep a close eye on these little tanks..because they are so little....but the fish have room enough to swim around..granted, not as much as a larger tank..but enough that they don't look cramped. I do plan on moving them into larger quarters when I can...but for now......they're fine !
If someone wants to keep fish, but doesn't have the room for a larger tank...I see no problem with betta bowls....but...I would definitly recommend a good substrate and live plants and keeping them in a place where the water temp can remain fairly stable. I have 3 one gallon betta tanks in one of the cubbies on my computer desk. With the tanks surrounded on three sides, plus the shelf overhead....the temp in that little cubby stays pretty even...(I have thermometers in each of the tanks) A well thought out and carefully cared for smaller tank (say, at least one gallon) can work out rather well if you are conscienceous in your care.