It's beyond frustrating.  I've referred to Quantcast, Alexa, Compete and Google Analytics for the last four years of my business.  I obviously trust Google Analytics data more on our unique visitor stats.  The others I've found to be practically worthless.  They each trend our unique visitors in different / conflicting peaks and valleys.  At a certain point there's just no value in referring to them. 

The problem with Compete is that it's U.S.-specific. So if your readers are primarily outside the U.S., it'll look like a ghost blog. Because everyone knows only the U.S. has blog readers... ;-)

 I use Quantcast, Google Analytics and then maybe Alexa or Compete. Alexa and Compete state that two of my sites dropped 40-50% in the last few months when Google and Quantcast show they went up 20%. I know that my visitors numbers went up & not down by the number of emails and form submissions I received along with the upward trend in CPU and Memory usage on my Server for the last few months.

Well to be picky, in March many news sites did see a large spike in traffic due to the epic and weeks-long news out of Japan.  That could explain the CNN spike you mention.

Do you use Stumbleupon?  I believe Stumbleupon skews numbers greatly with Google Analytics counting way more than actually hit your site. Just my thought. 

Hi Dave, It's Lindsey from compete Client Relations, we have been corresponding via our support email. I'm just checking in to let you know I'm working on the follow-up to your second round of questions. I'll be sending you a bit more information in a few. Thanks!

I've only taken Compete.com (and any other traffic determination site) as subjective, rather than absolute. The numbers mean nothing, but as another commenter said, the relationship between the numbers and the trends are what I look at. Hey, at least the variance between your unique visitors and visits have the same variance! ;)

 I have used Alexa.com to get rough traffic numbers on 3rd party sites in the past. Its never been something I have focused on, so I suspect some Pro's will have better suggestions. 

 I find resources like this are more research tools than analytics tools. The difference being that research tools are more for trending, finding direction, and supporting analysis. Analytics tools are more absolute; they have real data and figures from actual interactions. I don't think that compete.com would ever be a tool that will replace analytics since it is based on sampling.

 Hi Dave - Matt here, Client Relations Director at compete.com.  I am happy to do my best to clear up any confusion if you reach out to me at support@compete.com.  Compete is based on a sample of 2 million, US based panelists.  We have a small sample warning on your website, which means we have limited data on your domain.  Even when considering your GA numbers, you are well down the long tail of the internet.  The code you've installed, it is just for audience profiles and it is only found within that tab of the product.  It does not impact any traffic numbers.  In any event, I'd be happy to explain more if you would like to reach out.