This does not mean, however, that you can't use a CFC. Do no forget CFCs under web root can still be accessed via URL. Here is a very simple example:
<cftooltip sourceForTooltip="test.cfc?method=getsource&returnFormat=plain"> The content to be wrapped. The content to be wrapped.<br /> The content to be wrapped. The content to be wrapped. </cftooltip>
All I've done here is point to a CFC in my URL. The method argument just tells the server which CFC method to run. The returnFormat is important. If you leave this off, the result will be a WDDX string. Now this actually rendered ok in my browser, but you really want to use the returnFormat=plain to ensure a non-encoded response.