Photographers/Models like to maintain a portfolio featuring only their best work which sells them well to each other. When a photographer views a model's portfolio he expects to see a well thought out selection of images featuring her range of work at its best. I suspect the same is true of models looking at photographers' ports. Neither want to have to sift through a huge collection of sub standard imagery in the vain hope of finding something worth looking at. Inevitably the result is clicking through to the next model. For me in particular that often happens as soon as I see albums in a portfolio.
Picture collectors like to upload the entire set of images from a shoot and feature them much like a strip set on a porn site. Often as not a pretty low grade porn site - sorry guys but that's the truth. Having those images merged with portfolio images throughout the site, including all the image streams, muddies the waters at best when prospective new members wonder what the site is all about.
There is also a fair amount of rub going on between the picture collectors and the photographers/models.
It would make sense to me if portfolios were limited to, say, 40 images and EVERYONE chose only their best images for their portfolio. Any excess over 40 images should then appear totally separately in a collection of albums attached to the member's profile but badged appropriately - 'My Porn Collection' or something like that. Sorry, I meant to say 'My Picture Collection'!
You could then present two 'recent images' streams - one for portfolio images and another for picture collectors' images. I think doing so would remove some of the rub and it would also allow people to be more selective about the images they're presented with when they view the streams.
I would go further and say that the existing competitions should be restricted to images from portfolios only. However you might wish to create a separate set of competitions for the picture collectors.
I do realise that's a pretty big change and unlikely to happen in the short term (if at all) but I think it's worth airing.