Not really, I'm just curious and wanted to dissect a well-accepted method that we use and see what's really been tried with it... three part question.
1) I'm interested to know what trial-and-error process (if there was one, or if it's just 'because it's cheap/simple') led to film canisters being chosen as THE substitute brom, and what else has been tried.
2) Given the preference shown by some frogs for white or black over the other (racists!), have any other colors (particularly browns and greens which would mimic broms more closely) been tried? I doubt there would be any profound effect on egg-laying, but if it hasn't been tried it might be worth it with some of the touchier breeders. If little variables like the angle/placement/color of the film canister affect a fair number of species, there must be a possibility...
3) Along the same lines, has anyone noticed whether film canisters set into the background or covered with natural material (moss etc) are more likely to be laid in than free-standing containers? I would assume that some frogs couldn't care less, but some might.... benedicta's tendencies with the backward-facing cups comes to mind.