What are common problems people have with managing own PPC?

Poor click-through-rates (CTR)
No visibility of which phrases are generating real conversions on your site
Ads that repeatedly get disabled due to poor performance
Paying too high a price per click due to lack of effective bid management
Lack of time to properly review and manage the account and bids
Lack of experience with the advanced features that can drastically improve ROI and performance
Lack of knowledge and time to manage PPC advertising campaigns across several search engines