DISCLAIMER: I could not resist not to ask this question, although I know there is no single, objective answer. Please, delete it or turn it into community wiki.
As a potential employer, how would you respond to a cover letter with a list of genuine bugs found in his /her site or product?
This is just to present sample of applicant's skills (in bug hunting) by analogy to portfolio of
- photographs, when applying to a photography school / media agency
- open source projects, when applying for a developer job