This prediction by Eberhard is supported by Dixson (1987) who has analysed different aspects of penile morphology in primate species and found that size and complexity are indeed related inversely to the number of males that typically mate with each female. Thus for monogamous and polygynous males the penis is smaller and simple in design whereas in multimale/multifemale, or dispersed species, it is larger and more complex. Many species of birds are of course also monogamous which would further support this theory.
If true it seems that many Indian males have it good, a noncompetetive system to find partners and a system (caste) in which they automatically acquire some status.
Update 12.12.06: The BBC article mentioned above is still among the most e-mailed articles and it appears that Indian males may have interesting times abroad. Another article on condom sizes in BBC News, this time about South Africa.