If you are finding it difficult accessing the iPhone jailbreak app store then the recent tweet from the Saurik confirms that it is because of some connectivity issues arising from the Amazon’s EC2 cloud services.
Cydia uses Amazon EC2 service, which has been experiencing service outage for last more than 16+ hours. The problem is only affecting a few and its intermittent so you may not have experienced yet, but still the problem is there.
Now Saurik has tweeted about this Cydia issue saying:
Amazon EC2(which does not host the primary Cydia website, purchasing, ect.) is currently experiencing severe issues: nothing I can do but wait.
However, the Cydia is working fine on our end and if you are among the affected users then please do comment if you find that the problem is resolved.