The Microsoft Excel product team has listened to customer feedback and created the Manipulating Points on Charts (MPOC) add-in. MPOC provides Excel 2007 and Excel 2010 users the ability to resize or reposition points on charts. This feature was last present in Excel 2003 and later removed. Since then, customer feedback has shown this feature was used often and missed when it was removed. The Excel product team has responded with this add-in and they are assessing how to bring this back into a future Excel release.
See the announcement at the Microsoft Excel 2010 blog site along with complete documentation for using the MPOC add-in. Install the MPOC add-in here.