The idea is to allow an admin to create rules like this:
Date Field A.date-A of Entity A defines a period of time when Entity B is not available.
Entity A connects to Entity B with Entity Reference Field A.reference-B
When Entity C then tries to reference Entity B with an Entity Reference Field C.reference-B and defines a date range with Date Field C.date-A that is set within the time range defined by Date Field A.date-A, a validation error is thrown on save of Entity C, because Entity A has "reserved" or made Entity B unavailable in that time range.
The relationships are all configurable. Entity A and B could potentially be the same entity. The field relationships are all configurable as well, and a ctools multistep form wizard exists to help you get these complex rules set up.
Want to guard against spam? Want to make sure sensitive information isn't easily nabbed by an automated script?
Use Enkoder for Drupal! This uses the logic behind Hivelogic's Enkoder to encode any field or arbitrary text in a recursively self-evaluating block of javascript, foiling all but the hardiest of spambots.
You can use this to harden any text-based field and this module also exposes a general-purpose php function (sclib_enkoder) for your own custom uses.
In my examination of the Drupal module landscape, SPAM-hardening solutions either tend to be focused on forms (like CAPTCHA) or provide very limited email encoding (such as by providing HTML entity encoding or exposing an input filter).
By using this module, you
can arbitrarily harden any core text field, even ones that don't use an input filter
can arbitrarily harden any text, not just things look like email addresses.