Vague language is an interesting topic. I believe it is more common in speech than in writing, which means that it is more advisable to use spoken corpora for research of this kind.
Spoken language, and face-to-face conversation in particular, takes place on the basis of a shared context, avoids elaboration or specification of reference, and reflects the needs for real-time processing (Leech 2000). It is, therefore, hardly surprising that conversation is more vague than most written genres. Vagueness is pervasive in conversation where it plays an important role. The most obvious reason for using vague expressions is uncertainty at the time of speaking. In this case, vagueness allows speakers to maintain fluency even though they lack information about a given quantity, quality or identity, or, when such information is potentially available, they cannot access or process it in time. However, speakers may still choose to be vague even when they could in principle be more precise. This is because vague language can serve a number of pragmatic functions. Jucker, Smith and Lüdge (2003), for example, analyze the vague additives (i.e. approximators, downtoners, vague category identifiers and shields) and instances of lexical vagueness (i.e. vague quantifying expressions, vague adverbs of frequency, vague adverbs of likelihood, and placeholder words) in a corpus of semi-controlled spoken interactions between students in California. They find that vagueness is an interactional strategy which plays an important role in managing conversational implicature. First, vague expressions may serve as focusing devices, directing the hearer’s attention to the most relevant information. Second, vague expressions of quantities provide information about the significance of the quantity and may provide a reference point in terms of a scale. Third, vague expressions may also convey several aspects of propositional attitude (e.g. conveying different levels of certainty regarding the propositional content, conveying the newsworthiness or expectedness of a statement, and conveying evaluative meaning). Finally, vague expressions may serve various social functions (serving as politeness strategies, softening implicit complaints and criticisms, and providing a way of establishing a social bond). As such, vague language helps to ‘guide the hearer towards the best interpretation of the speaker’s intention’ (Jucker, Smith and Lüdge 2003: 1766).
For Neil Drave's paper, see
http://www.corpus4u.org/showthread.php?t=344
Jucker, Smith and Lüdge's paper is here:
http://www.corpus4u.org/upload/forum/2005080818035159.pdf