Although the proposal in comment #11 has merit, in the end what the user wants is *predictability*, not that some rules that he does not know about might be lucky and do what he wants. There are myriad of reasons that might make those rules fail and do not do what the user wants.
What does someone expect when buying a new phone? IMHO:
* One SIM inserted -> The user wants to have data activated
* Two SIMs inserted -> The user wants to have data activated for one SIM, but probably not for the other (the "secondary" SIM tends to be used just for calls/SMS). The problem is that we do not have a clue on which SIM does he want to use for data, as the reasons tend to be "main operator vs operator for doing some calls SIM" or "work vs personal SIM". Besides, we know which is the main slot, but that is not obvious at all looking at the phone, so the user might have inserted what he considers the "main" SIM in any slot. In this case, I would say that the right option is to let data off for both SIMs until we have a wizard that lets him select the SIM for data on first boot. The user that has inserted two SIMs on the phone is probably knowledgeable enough to go to system settings and choose the SIM he wants for data.
To summarize my proposal:
One SIM -> Data on for that SIM
Two SIMs -> Data off for both
Although the proposal in comment #11 has merit, in the end what the user wants is *predictability*, not that some rules that he does not know about might be lucky and do what he wants. There are myriad of reasons that might make those rules fail and do not do what the user wants.
What does someone expect when buying a new phone? IMHO:
* One SIM inserted -> The user wants to have data activated
* Two SIMs inserted -> The user wants to have data activated for one SIM, but probably not for the other (the "secondary" SIM tends to be used just for calls/SMS). The problem is that we do not have a clue on which SIM does he want to use for data, as the reasons tend to be "main operator vs operator for doing some calls SIM" or "work vs personal SIM". Besides, we know which is the main slot, but that is not obvious at all looking at the phone, so the user might have inserted what he considers the "main" SIM in any slot. In this case, I would say that the right option is to let data off for both SIMs until we have a wizard that lets him select the SIM for data on first boot. The user that has inserted two SIMs on the phone is probably knowledgeable enough to go to system settings and choose the SIM he wants for data.
To summarize my proposal:
One SIM -> Data on for that SIM
Two SIMs -> Data off for both