As described here http://documentation.magnolia-cms.com/modules/form.html#Disablingcache, starting with Magnolia CMS 4.4, individual form pages and the first page of a multi-step form need to be excluded from cache to prevent "session expired" errors. This has major disadvantages for people using forms in a simple Magnolia setup:
1. It doesn't work out of the box: The person setting up the Magnolia has to know about disabling the cache, which might be overlooked and not caught by rudimentary testing since the "session expired" error only occurs with IE (right?)
2. Editors have to be told not to change the names of the form pages or report their renaming, so that the caching rules can be adjusted. Of course this could be checked and adjusted by scripts, but in a simple setup that would exceed the budget available for CMS development and configuration.
Therefore, I would vote for requiring the cache-disablement only on multi-step forms, that are more complicated than a simple contact anyway.