I can see an argument for separately counting positive and negative votes. An article with +100 and -100 is likely to be... well, not the same as an article with no votes.
But I do think negative feedback _is_ effective and useful. Like or not, there's plenty of posts on an open forum that are themselves negative. Be that via trolling, offensiveness or merely being offtopic. It works quite well with Slashdot - being able to filter based on threshold values is also a valuable way to efficiently filter wheat from chaff.
I don't think removing anonymity is particularly beneficial - it's not exactly difficult to re-register on most sites, and a contribution is valuable regardless.
