Funny how only a few years ago nothing short of a medium format camera loaded with high quality ISO 160 film was good enough for a wedding but now many people are shooting with a crop body SLR. Why have IQ standards fallen so much? Is it that the buying public doesn't care much about IQ or it it that price pressures have reduced prices so much that photographers cannot longer justify the price of high-end equipment. I'd thinking it mightbe a little of both. Clients don't can't tell the difference in small prints and the guys doing the $100 wedding packages have made it impossable to complete if you have a $30K camera system to support.
False.
Film silver hallide particles are about 2 microns in size whereas a 40D (for example) has pixel sites that are 5.7 microns in size. HOWEVER, a single silver hallide particle can only represent 2^1 different tones (it's binary - either "exposed" or "not exposed") whereas each digital camera pixel can represent 2^16 (65536) different tones. You need a clump of about 30-40 silver hallide particles to provide the same tonal information as a single digital camera pixel. So while film still slightly edges digital in spatial resolution, unless you're taking pictures of black and white resolution charts all day and want to, I don't know, take pictures of people and flowers and landscapes and such, then a digital sensor annihilates film in terms of real-life image quality.
Of course, you'll immediately argue that that statement only applies to sensor and film of the same size. That's true. But even considering the fact that medium format film is 8 times larger in each direction than a cropped sensor, you still arrive at the conclusion that medium format film and cropped digital provide about the same amount of image quality in terms of real-life resolution.
Back in the film days of wedding photography, of course professionals used medium format because it is vastly superior to 35mm. However, digital now reigns supreme in wedding photography because of its superior image quality and flexibility.
Now that that's out of the way, any photographer worth their salt will tell you that the sensor has little to do with image quality in terms of resolution compared with lens quality. Very few lenses except some L-series primes can provide a point spread function smaller than the size of a single pixel at a reasonable aperture throughout the frame anyway, so increased pixel density is just going to waste anyway.
Cropped and full frame sensors have their tradeoffs. Cropped uses only the central portion of the image field, which presents an advantage over full frame because all 3rd order aberrations (coma, astigmatism, field curvature, and distortion) except for spherical aberration are field dependent (meaning they get worse as you get closer to the edge of the field). On the other hand, cropped sensors typically have a higher pixel density than full frame so you're trying to collect more pixels with less field information.
Sorry for that long rant. At any rate, I think we can all agree that wedding photography is 10% equipment and 90% skill. I've seen amazing pictures come out of a Rebel XT, and I've also seen crap from photographers who use a 1Ds-III.