Why should I focus on long-tail keywords instead of short-tail keywords?

Short-tail keywords are generic and highly competitive. Long-tail keywords attract fewer visitors individually but those visitors are more qualified and specifically targeted. Summing all long-tail keyword traffic can in theory outperform a single short-tail keyword in both volume and conversion quality.

Short-tail keywords are generic and highly competitive. Long-tail keywords attract fewer visitors individually but those visitors are more qualified and specifically targeted. Summing all long-tail keyword traffic can in theory outperform a single short-tail keyword in both volume and conversion quality.

From SEO 2010 Year in Review Part 1 - Internet Marketing Podcast - Number 89

Long tail keywords (three or more words) attract searchers who are more specifically looking for your product or service. Short tail terms like 'lawyer' attract broad research traffic, not buyers. Someone typing a long phrase like 'personal injury lawyer in Houston Texas' is far more likely to need your specific service.

From iPhone iPad SEO and Keyword Stuffing - Unknown Secrets of SEO E-Webstyle Number 61

Use both but approach them differently. Long tail keywords deliver faster, more relevant results and should be pursued first to show early ROI. Short tail keywords are harder to rank for and require more budget and time but can deliver broader traffic long term.

From Keywords and Twitter, What to do with both? - #seopodcast45