Where I'm working now, most of our old code didn't use placeholders and binding. Now that we are literally doing 1000X more transactions then when the program was written, we are feeling the pain. We've gone back and started to change all of our old code, and it has made a huge difference. Not only are we able to keep up now, but the program now responds noticeably faster then it did before. I see using placeholders and binding like using strict and warnings, you may not think you need to use them, but if you don't use them, it will come back to haunt you.
PS We use an Oracle database.
PPS We are doing this to both our perl and java code, and both languages are benifiting from using placeholders.