Generally speaking, Font Linking (for example, @font-face) will violate EULA for the font used because it is based on the redistribution of the font file. Ergo, you can't. Of course, there are fonts that allow this.
Hoefler and Frere-Jones mention sIFR in their FAQ in paragraph 20: http://www.typography.com/ask/faq.php . To summarize, they are fine with him if you take all possible measures to prevent reuse of the Flash file. I have not seen this from other foundries. However, the Flash implementation should be known by now, and IFR / sIFR is about six years old, without any lawsuits that I know of.
Cufón, Cufón . , FUD "" sIFR, .