Mass Exodus from Canon?

In the last months talking to different photo-equipment dealers I have heard of several customers switching from Canon to Nikon, specially when they have older Canon bodies (and where willing to update their body anyway).

Is my current impression right that there actually are many Canon customers moving to Nikon? And if yes, which is the main cause:

(a) The current consumer (400D, 40D, 5D) lineup does not offer enough
compared to other brands

(b) Nikon has currently a better marketing campaign

(c) Canon has done crucial marketing mistakes like waiting too long
for a 5D successor

(d) Canon has frightened customers away with their handling of the
MK III AF problems

(e) Other?

Carl