Rather than negotiate with the PA, Sharon chose to make a unilateral withdrawal from Gaza. His intent was clear. To reduce the costs of Occupation, which he achieved. His other intent was to not deal with the PA. Which he also accomplished. But what was not provided for was the ability of the PA to deal with the reduction in security caused by the removal of Israeli forces deployed in Gaza. When Dahlan attempted to crush Hamas the counter-coup left Gaza under the control of Hamas. The danger of 'unilateral' is that it leaves too much to chance in a volatile situation.
Texas Southern University on lockdown, gunman sought after 2 shot at student housing (AP)
from the article: Palestinian PM: Declaration of statehood just a formality