I have to comment in support of Rainboe, 411a and Nigel on Draft. As carefully trained and checked professional airmen/women, we are given responsibility and the ability to safely operate our aircraft, on a daily basis, without technical input from the cabin. The ability to do that is at no time more evident than when just 2 pilots ferry an empty B744 around the skies for air-test or maintenance. Our ability to operate is not at all dependent upon input from the CC but, as indicated elsewhere, they are useful eyes and ears in the cabin and their concerns, even if unfounded, should not be ignored. However, the 2 posts from quartermilltopo and Desk Jockey only serve to show how flight regularity and even safety, due to distraction, might be compromised by false cries of alarm from untrained and ill-informed observers.
It seems that many posters here are unaware that it is the failure to set the SLATS for takeoff that is lethal.As observed, the A300 often uses no FLAP for takeoff, but I am not aware of any large commercial transport that does not deploy SLAT (or LE devices) for takeoff. It is extremely difficult, on some types, to determine by observation from the cabin if the slats or low angle flaps are selected, even in good viewing conditions.
At the end of the day, it is strict checklist discipline which will ensure that all is correctly set, particularly under stressful circumstances away from the norm, such as a taxi back and return for takeoff.
On my current type and with my current airline, but also with 2 previous operators, we are not permitted to commence taxy without the slats and flaps being selected first. They are selected as part of the 'after start' procedure, prior to brake release. Some operators even have a FDR 'event' marker triggered if this procedure is not followed. A further back-up is that the ECL ( electronic checklist, for SLF) will not allow the takeoff checklist to progress to completion until the takeoff configuration is correct. This is an excellent safety measure which prevents misconfiguration should the flap/slat deployment have to be delayed in icing conditions, or get forgotten for any reason. Perhaps all aircraft should have this technique and ECL as SOP.
The ultimate backstop is a check as suggested by 411A. We used to call it a 'seniority check'. Mine is flaps/slats, trim, power setting, speeds.