I've seen smart people fall into the following trap: 1. Previous developers did X and X is bad, therefore, their code needs to be rewritten without doing X. 2

I've seen smart people fall into the following trap: 1. Previous developers did X and X is bad, therefore, their code needs to be rewritten without doing X. 2. Oh crap - turns out, the new code has all these requirements to match the old code's functionality in ways we didn't expect (letters A-W). 3. Okay, so we're doing Y and Z in the rewrite, knowing it's pretty bad, because we didn't know we'd have to do A-W and now we're short on time. Oh, and parts of the code still do X. Now, wait a year for one third of the team to leave because they're rushed, overworked, burnt out, going in a different direction... and another third to get laid off because the project went way over time and budget... 4. Previous developers did X, Y, and Z, and X, Y, and Z are bad, therefore, their code must be rewritten...