The rapid growth of South by Southwest’s Interactive portion is raising concerns over the event’s ability to effectively launch new tech startups. 28,000 attendees are expected at this year’s portion, a jump of 9,000 people from just two years ago. The festival has formed a tradition over the last five years of providing promising startups with a large-scale launch platform, and the model worked for current mainstream hits Twitter and Foursquare. With no early favorite emerging before the festival, concerns have been raised that the sheer scale of the festival may prevent any single entity from emerging as a fast favorite, taking away much of the saturation effect that launched favorites in previous years. Of course, we’ll only know what emerges next week as SXSW runs its course for 2013.