Duplicated code :

Copy Paste is most probably the single most expensive operation when it comes to maintenance costs of programs.

Why bother move this code to a common component, i'll just copy it over and be done with it Yes... the programmer probably saved an hour of work or so doing things this way. However later comes a bug and... yes of course it gets fixed in only half of the running code. Which means that later still a regression will be logged resulting in yet another fix OF THE SAME THING.

This one sounds obvious but in the grand scheme of things it is insidious. Programmers look good cause they get more done. Dev team manager look good cause they delivered on time. And since the problem is found only much later blame never befalls on the real culprit.

I lost count on how many times I had to halt a release because of such "regressions" Just now I lost one full day tracking a fix that was already done, get it fixed again and pushing the new build through the hoops. So yes, one hour time for one dev six months ago (approx CAD 40$) just costed one full day for 1 senior dev + half day for one junior dev + one full day delay in a project already late....

you do the math....

so next one that pulls this on me I swear he'd better run fast caus'i'll be right behind him !!!