As much as people cut down on MSN Adcenter, I actually like it; for the most part.  Relative to Google, they are quite small.  But bids are much lower, conversions are decent, and you can still make a lot of money with Adcenter.  The thing I hate most is their ad disapproval system.  When an ad is denied, I get notified a couple days later by email with a huge list of ads and keywords.  I wish they had a notification that appears at the top of the campaign name so we, as the advertiser, knows exactly when an ad or keyword was denied, and which keyword or ad was denied.  It is frustrating to find out that 50% of your traffic for a keyword is gone because an ad was disapproved for some stupid reason.