I felt guilt when I couldn't BF DD.
I would say that most of my guilt came from two areas. Concern about what other people would think of me, and also overplaying (in my mind) the benefits of BF.
I don't intend with that latter comment to get in to a debate about the various virtues of BF and FF, but my opinion about the benefits of BF has changed since that time. I believe it to be 'optimal' as is often stated, but I think I had an exaggerated regard (back then) for the health differences that it would make to DD.
Now, with a 2nd baby imminent, I will try to BF again but do not believe I will feel guilty if I don't succeed. I believe that I now have a more realistic understanding of the processes involved, and I don't think that the benefits of BF are as significant as I previously did.