Lately (November, December 2014) the #1 cause of "Hosting account resources exceeded" emails is what we call the "404" Attack Bot.
This bot scans websites looking for URLs associated with plugins that have, or have had, vulnerabilities. Quite often, the website being scanned does not have any of the plugins installed so it generates a large number of 404 response codes (not found) -- hence the name.
The bot may trigger an EP alert due to the large number of URLs scanned in a short period of time. The effect is much like a brief denial-of-service (DoS) attack.
The bot is relatively harmless, assuming you keep your WordPress and plugins updated. The DoS is very brief.
But ...
We recommend installing WordFence to protect against this bot. A nice bonus is a top-notch cache you may use in place of WP Super Cache or W3 Total Cache.
We do not recommend upgrading to the commercial version of WordPress. The free version is sufficient for that vast majority of users.
WordFence configuration can be a little intimidating. Feel free to contact support for a "token" that will setup WordFence with our recommended configuration.