'Cause it's the most frequently sold car, and thus there is a huge market for parting them out into spares (plus, a huge pool to choose from). Ease of disposal of stolen cars isn't even linear with amount sold, it seems more like exponential, because chopping them up has such a lot smaller chance of being jailed than selling them whole -- and yet, parting out a Ferrari Enzo is not all that profitable. So, even compensating for sales figures Camrys get stolen more often. You also hear that thieves nowadays, with sophisticated anti-theft everywhere, tend to specialise in one brand, type, or even model year. If you only steal 2002-2004 Toyota Camrys, you can get *really good* at doing it.
Jasper