Recently a question came up about using $Action.Contact.AddToCampaign on a Visualforce page. The common usage pattern below for $Action variables does not work as expected.
So, I logged a case with Salesforce to get an explanation for how $Action.Contact.AddToCampaign is supposed to work. And the eventual answer I received after three weeks was very surprising.
In short, the merge variable only works when used as the action value in a form element. Let me illustrate this with the sample Visualforce code below.
The unfortunate answer at this point seems to be that $Action.Contact.AddToCampaign only works if you want to use it inside a custom HTML form, not an apex:form. salesforce.com's recommendation is to use $Action.Campaign.AddCampaign instead, which in my opinion defeats the purpose of easily launching a native wizard to add the contact in a given context to a user-specified campaign.
