Electronics 'Hacking' seems to be a new thing - to me at least - anyone else know people like that?
You can get away with some stuff by "rule of thumb"; ie, using 220 or 330 ohm current limiting resistors for LEDs, using 470 ohm to 1K base limit resistors on transistors, if things get too hot, add a heatsink, change the resistors to higher values, use a larger transistor.
Good enough to get a working circuit on a breadboard, but not for something permanent. For that, one should really think about what they are wanting, look at the datasheets, and do a real design.
Basically what your friend is doing is similar to what you see in the software development community; there are some that just "hack it together", and it typically works; maybe even beautifully - but woe to the next programmer who has to add something or maintain it in some manner. Generally there is a huge lack of comments or any other documentation for the code; sometimes the code can be so arcane it can feel like how the person who wrote it "thinks".
Then there are those who ask questions, plan the process out, write pseudocode, document the process flow (perhaps with flowcharts), designs the GUI and functionality, etc - long before the actual coding starts; then when they code it, they take notes on the code, add comments that make sense and describe what is going on (as opposed to comments that say something like "this sets the variable xyz to i+1" - as if you couldn't see that) - and generally, what comes out of the process is close or identical to what was designed. It may still have bugs, but the next guy to come around to coding on it won't have as big of a problem deciphering it.
Now - if your friend starts to play around with high-voltage circuitry, or messing around with TVs or CRTs - watch out. If you don't know what you are doing there, you can easily send yourself to the hospital, or to the morgue.
