Yeah it does that is why it is recomended that you put a 301 redirect at http://daniweb.com to http://www.daniweb.com
Why? You combine your page rank from two sites (daniweb.com and www.daniweb.com) into one, ultimatly will pass on more PR to your sub-pages, hence, better SEO.

I think it does sometimes but not always... like when John Scott moved his forums to a new domain they took a bit of a hit. also 301 redirects surely will get abused a bunch more going forward. I think on same domain they should have a tendany to usually do fine but some cross domain ones might not pass their full value. I do not have much experience with 301s though

Can you elaborate?

According to seobook's book, beware of 302 redirects.

I've seen people report mixed results with using 301s. I highly recommend that you 301 redirect example.com to www.example.com on all your sites. But as far as a totally different domain, I would only do it as a last resort.