This seminar explores how language is used to build community with the microblogging service, Twitter (www.twitter.com). Systemic Functional Linguistic (SFL), a theory of language use in its social context, is used to analyse the structure and meaning of ‘tweets’ (posts to Twitter) in a corpus of 45 000 tweets collected in the 24 hours after the announcement of Barak Obama’s victory in the 2008 US presidential elections. Using this analysis I suggest how tweets function to invite a digital audience of ‘followers’ to share in evaluative bonds (Knight 2008). The paper shows how the hashtag, a typographic convention on Twitter, has extended its meaning potential to operate as a linguistic marker referencing the target of appraisal in a tweet. This both renders the language searchable and is used to upscale the call to affiliate with the values expressed in the tweet. Using hashtag usage as evidence, I suggest that we are witnessing a cultural shift in electronic discourse from online conversation to what I term ‘searchable talk’. I will also briefly explain my current work building a 100 million word corpus of tweets for larger scale corpus-based discourse analysis.