The flaw in your example is that the pizza delivery guy witnessed the crime. Blackberry in these cases, did not witness, then report. They are simply being asked to blow the doors off the safe that may contain some information of interest. Even that isn't necessarily a problem. Law enforcement might want to contact the safe company and ask for their assistance to make sure the doors are blown off without damaging the contents, and the safe company engineers might be the best people to help achieve that.
The problem with cases like these is that they are increasingly being requested without the proper legal documentation/subpoena that would allow the evidence to be admissible in court. They are being used for fishing purposes. Information that they could use, then use other methods to verify the information obtained. For example, guy suspected in a murder case. They want data from the phone. The person of interest denies the request. Subpoena is requested and approved for the person of interest to turn over any information relevant to the issue at hand over to police. The person of interest refused and is found in contempt, then sent to prison. The manufacturer is asked to unlock the device so police can look through the device for evidence. The manufacturer, in this case, Blackberry complies. Now police have access to everything on the phone. Including a text message sent from the person of interest to someone else with evidence of a robbery that was committed 2 months prior. Now, since the subpoena didn't cover that prior crime, they can simply get a new subpoena for the recipient's device to have that message now meet the legal conditions required to be considered evidence to be used get an indictment on that unrelated crime.
What's the problem with that? I see that as a violation of the person's 5th amendment right against self-incrimination. But it is happening more and more frequently. With mixed results when being fought in court.