It's hard to say, but I just did a write up about what we saw in our data: <a href="http://reviewsignal.com/blog/2013/08/03/service-interrupted-a-look-at-the-eig-bluehost-hostgator-hostmonster-justhost-outage-through-twitter/" rel="nofollow">http://reviewsignal.com/blog/2013/08/03/service-interrupted-...</a><p>tl;dr: companies have outages, big ones seem to regress to the mean. There are companies that are liked a lot more though.
<a href="https://twitter.com/hostgator" rel="nofollow">https://twitter.com/hostgator</a><p><a href="https://twitter.com/bluehost" rel="nofollow">https://twitter.com/bluehost</a><p><a href="http://enduranceresponse.com/" rel="nofollow">http://enduranceresponse.com/</a><p>Looks like many sites are coming back online.
It appears to be a network issue that is affecting all of them, I would therefore assume that it's an issue on their upstream transit providers, or if they share a data centre then it could be a localised network/power issue.