So many of them .... and in most, the same problems occurred again and again about unrealistic time-lines (not supported either by past projects or provided by the dev/qa/db teams), requirements changing until the last minute, testing in the same time with development, no risk analysis, etc.
These things repeated so much in my past experience that after a while, all of them became the norm, so normal.
You get so used to them that you don't see them as wrong after a while.
This is why it is refreshing to find an article like the one from below with the top worst software development mistakes, compiled in many years of experience of the author.
I am still puzzled of why software development projects cannot be better but at least, I know now that what I went through is not an exception but probably the rule.
This is the article on software development worst practices written by Gregory Pope and published, where else, in the Better Software magazine: