For me,the order I'd put these things in would be:

Conflicting advice after birth
Lack of education
Lack of continuity of care
Interventions at birth
Family and friends ideals/ advice/ expectations
Lack of affordability/ availability of care
Accessibility of artificial milk
Health professional influence
Going back to work with lack of bf support
Marketing of artificial milk

For me the main problem I had was that due to illness my milk didn't come in properly after my DD's birth. I tried to bf her after a few days (I was too ill in the first three days after she was born) and the midwives were no help. They all told me that my milk would come and to keep trying to feed her, until then supplement her with formula. She would scream and arch her back when I tried to attach her and I ended up with really badly damaged nipples. One midwife said to try to perservre which I did and DD ended up with a tummy full of bloody milk which she promptly projectile vomited all over me. I was horrified. After this another midwife said to stop bf until my nipples were a bit better, so I did and ended up with slight mastitis. I was a mess, which wasn't helping with my milk production.
It wasn't until about 5 days after my DD's birth that another midwife suggested and arranged a lactation consultant to see me, as well as a social worker. The LC said my DD was attaching and sucking really badly, even though the midwives were telling me she was doing well. And also that my holding technique was also quite bad.
The LC gave me a pump to use to try to increase my milk as well as some medication to help. She showed me how to hold DD properly and how to attach her and breast shields to use in the meantime to continue bf with horribly blistered and sore nipples. She saw me twice in hospital and then arranged for another LC to see me at home twice. I ended up with engorgement for a few days and DD was really difficult to get on the breast, anding in blistered and sore nipples again.
In the end though I have been unsuccessful in bf DD. My milk has decreased after a few weeks, and we also ended up with thrush. I also suspect I may have something wrong to do with my letdown (though I am no Dr!). My DD was distraught and so was I due to her being starving hungry. My local Dr. told me to give her a bottle after bf, which I did and this helped. She did not give me any info. to help increase my milk production or anyone to call for help. My family did not support me in bf, with my DH just as distraught as my DD and I and wanting us to be happy, and my mother telling me she had so much milk it squirted everywhere and she fed all the premi babies at the hospital when we were born- maybe I just wasn't made to bf like she was.
When DD settled after being bf and bottle fed, avaryone pressured me to bottle feed her. She also began to reject me and only want a bottle (she's a lazy bones- too lazy to suck properly!). SO now here we are 5 weeks later, DD is almost fully bottle fed with only about 3-4 partial feeds a day being breast milk, supplemented with a bottle. At these times she has nearly a whole bottle so I think she only takes the breast for comfort more than for the milk.
I think that midwives need to be educated more or that Lactation Consultants should be at all hospitals for mothers to learn about bf straight away after birth. Going through all of this has really turned me off bf my DD. I know that even now I could probably increase my milk and get her solely on the breast, but with all of the trouble I went through, I am scared to do it and think it is easier (and will keep me more sane) to just continue with the bottle. There should also be more education (free!!) for pregnant women to prepare them for the trials of bf. I was never prepared for how hard it really is.