i guess it depends on how 'serious' one is about photography. flickr doesn't make a very good portfolio site, but i think any photographer can benefit from the exposure. i don't make any money and mostly just do it as a hobby, so i just post everything i like there. and i can't help but think that flickr is the reason i get like 300-400 visitors to my blog for every silly post i make. but as a distinct portfolio to show off the best of your work...there is just too much going on and there are too many distractions. it's a constant stream of jumping from one photo taker to the next, through different groups, etc. I rarely am able to browse through one user's stream for long, unless it's someone i really, really like. but, how can you not want to take advantage of the discovery factor? the sheer volume of users opens you up to so many more possible fans/sales, at least as an introduction to your work and maybe then they will follow a link to your actual portfolio/sales site (and, honestly, i discovered toycamera.com through flickr, which lead me to all of this). and i confess to being a mostly lazy internet user. i like things to be obvious to me at first, then maybe i'll do some more digging. and googling photography isn't any nicer than using flickr, for sure.
as for the whole yahoo thing, i haven't found it has changed much since the switchover. the censorship thing is odd, but it never prevents me from veiwing anything. i've NEVER found a single 'static' shot that ended up being offensive...like, they are always just regular photographs. yet i see 'penis in hand' shots in my all users stream all the time, so it is definitely a broken system. anyway, feeling chatty this morning.