Ok, born and raised Campbell style CoC here, so we were the poster child of baptism being required for salvation.
I no longer hold this view. I am pretty open / unorthodox here.
I can see both sides of this conversation. I really like the description above as Paedo = opt out; Credo = opt in.
I still lean towards the Credo view. I think that baptism is a beautiful confession of faith and symbol of what salvation means in Christ. A child cannot confess faith. One other point is that Jesus was baptized as an adult, and John the Baptist proclaimed that he should be baptized by Jesus. So, even if Paedo is practiced, why not Credo as well?
However, I am very sympathetic with K2's view of salvation happening as a family unit. Dedicating your child to a lifetime relationship with God at birth is also a beautiful thing. Dedicating a family unit to God can be powerful for everyone involved. I don't see why baptism would be inappropriate for this type of commitment.
Also, baptism wasn't really a new invention brought to us by John. The Jewish tradition is to have a place for ritual purification through water. Leviticus requires ritual purification, as does the oral jewish tradition. The place for ritual cleansing through immersion for Jews was the mikvehs, which were often built before even the synagogues were when Jews migrated to a new place. We witness miracles in these pools during Jesus ministry. The OT traditions of circumcision and animal sacrifice fell away, but baptism persisted, even though it took on a new, more important meaning. John taught a baptism of repentance for remission of sins, but, in my mind, it is hard to separate the context of Jewish immersion for ritual cleansing during Jesus ministry when looking at the importance of baptism today.
I guess where I come out on this is probably more in line with churches in the great awakening period. I wouldn't mind seeing lines of believers headed back down the river (think Oh Brother Whereart Thou) periodically to confess your faith again, and remind eachother of the state of salvation that we are in, especially in situations where you have people returning to the church after a period of struggle. Of course, the largest argument against this is the discussion in Acts 19, where there was some consideration whether or not the men in Ephasis needed to be baptized again. It is clear that they needed to be baptized into the name of Jesus, even though they had received John's baptism. One might infer that this means that only one baptism is ever really helpful, and should only happen once, but I'm not sure that might be reading too much into the text.
Net, net, I'm not sure it matters all that much when, but it is very, very important, clearly commanded, and can be a very beautiful and powerful symbol for all that participate and witness.