Well Bill that was part of the Shell problem, Pipeline safety etc is also important factors. Then of course you have the debacle of what Shell was accused of in the Niger Delta at Otuegwe, where they left untold ecological damage by using crappy methods of cleaning up (forest burning etc). Nigeria was in serious ecological trouble from oil spills by insufficient safety standards, all operated by Shell in the 90s. Nigeria provides I think over 10% of Shell oil and Shell in turn gives Nigeria over 70% of all its oil export revenues. In the 90s, nearly 40% of all oil spills in Shell's history happened in the Niger Delta.
Google Shell and the Niger Delta and you'll find a plethora of reasons why Shell embarked on a greenwash campaign in 2000.
Not that most other oil companies are blemish free.