When I first discoverd bloglines, I subbed to both slashdot and the register, and after about 2 weeks and 1976 unread items, I unsubbed and went back to browsing the sites directly every few days.

I think the salient features of these sites is:

1) you don't need to have new posts pushed to you cos you know there'll be a whole heap every day.

2) you probably will only want to read only 10% of the stuff that is posted.

3) Even the 10% you do read, you will only read when there's nothing better elsewhere.

In other words, sites with multiple voices tend to have higher quantity and lower quality.

The counter example would be the sorely missed suck.com.