I'm having this problem for the past week. After less than a minute on the newsfeed, this message pops up at the top: "This webpage is using significant memory. Closing it may improve the responsiveness of your Mac." Activity monitor shows facebook using over 3GB of memory on my 8GB laptop. I've tried many ways to circumvent the problem to no avail. One thing I CAN do on FB is look at individual pages. If you find a way around this, I'd love to know.