In addition to facilitating discovery of topical trends (Gardner et al., 2010), topic modeling is used for a wide variety of problems including document classification (Rubin et al., 2012), information retrieval (Wei and Croft, 2006), author identification (Rosen-Zvi et al., 2004), and sentiment analysis (Titov and McDonald, 2008).
regularization allows us to add something which is mathematically similar to priors, and has been shown to improve the vanilla anchor word algorithm (Nguyen et al., 2014).