I think the confusion here was assuming that the toilet and drain cleaners were containing lye, most actually are acids which when mixed with either bleach or ammonia products will produce a harmful gas. (see msds links below)
Bleach and sodium hydroxide mixtures are not a problem. I don't necessarily agree with chris's post about sodium hydroxide being a by-product of the manufacturing process but it is used to stabilize the pH of the bleach.
In the outdoor formula, there is no more Sodium hydroxide than the regular bleach but there are other surfactants added to enable the sodium hydroxide it does contain to be active otherwise it is classified as an 'inert ingredient'.
http://www.thecloroxcompany.com/prod...leach0505_.pdf
http://www.thecloroxcompany.com/prod...leaner6-07.pdf
Compare for yourselves.
http://www.hescoinc.com/Msds/ly74278.pdf
http://www.hescoinc.com/Msds/ly94201.pdf
Mixing bleach and sodium hydroxide together is a powerful oxidizing agent not to mention corrosive as well. The following link is for pdf based msds on drain cleaners for example.
http://www.scjohnson.com/msds_us_ca/drano.asp
Hope this helps to answer some questions.
Rod!~