According to the
"Ad Sweeper" extension page, all it can do is HIDE the ads, due to limitations to what javascript extensions can do. Also, it crashes occasionally I hear. So if those are enough problems for you to not try it, then don't get it.
QUOTE said:
Note: I do know it only hides ads. It's impossible to block ads like AdBlock Plus for Firefox does. Any extensions claiming that they do block ads are lying.
The reason for this is because Chrome extensions uses Javascript, and it's impossible to block connections through Javascript like it's possible using native code in Firefox.
Some people recommend AdThwart which blocks some ads from loading/connecting to while Ad Sweeper can HIDE the others AdThwart can't block.
On the good side, XMarks for Chrome is now Beta so that's pretty cool. If you still have the ALPHA, you must
manually update it (no need to uninstall) at this page.