What are the limitations of PCR technology?

Despite of the widespread application of PCR, this technology has some limitations:

• PCR cannot be used to amplify unknown targets. Prior information about the target sequence is necessary to design the primers.
• DNA polymerases are prone to error, which potentially causes mutations in PCR products.
• PCR is very sensitive to contamination. A small amount of contaminating DNA could result in misleading or ambiguous results.