On impact factor

We recommend that the term "impact factor" be abolished and that this measure be renamed in keeping with its actual role, that merely of a time-specific "citation rate index" and nothing more. What is currently called the "impact factor" should not be misused to evaluate journals or to validate the scientific relevance of a particular researcher or research program, especially in decisions regarding employment, funding, and tenure.

(from The journal "impact factor": a misnamed, misleading, misused measure by Hecht F, et al.)

Impact Factors reflect the journal not the article, vary with time and correlate only poorly with perceived excellence. Simple comparison of impact factors in different specialties may be misleading. Review journals often have higher Impact Factors than those with original data. Both authors and editors can try to manipulate journal Impact Factors

(from Impact factors: uses and abuses by James Neuberger and Christopher Counsell - pdf)