With personal data in hand, thieves file early and often. 

Forget drug deals, Florida criminals are trading guns for for laptops: With social security numbers and corresponding names & birthdays, criminals are able to file fraudulent tax returns before the real people file their legitimate ones. In 2010, the IRS detected 940,000 fake returns (worth ~$6.5B in refunds), but missed an additional 1.5MM possibly fraudulent returns worth more than $5.2B.