Can I drive a 5v LED direct from an I/O pin (without a current resistor) or do I have to have a current resistor to avoid problems?
Can't we simply answer the original question without all this I'm so much smarter than YOU are crap Or -I've sold ten thousand units breaking all the BASIC electronics rules, and got away with it thus far?

Was the original question asking about how smart you are, or asking if he could drive a single LED without a damn resistor?

I'm really glad that you managed to sell a TON of el-cheapo units without current limiting resistors. But the 100K that we have sold (with current limiting resistors) will still be ticking along even when the power-glitch causes a processor to HANG and hold that single LED ON until the user resets power...;o}

With our product, the user simply resets power, and it's all good. With your design, the user's forced to buy another unit. It's toast if it hangs when directly driving an LED. The customer that's buying your product doesn't give a damn how smart you think you are. They just want a reliable product that works well beyond whatever you state the warranty period will be, and that's exactly what we aim at. Our stuff works well beyond the warranty period.

We prefer to design-in protection against all failure options, and provide our customers with the little bit extra for a product that simply works

Of course, it would be in our best interest to sell them a new unit every six months or so, but, as a consumer myself, I think that approach sucks. I would rather sell our customers a unit that works forever. And if this means including an extra resistor or two, then we're totaly OK with that.

If it's got a warranty period of 2 months, we'll expect it to last 12 months. And, we would never consider calling anyone stupid, or laughing about anything someone had done in the past.

I think it's just plain arrogant of any real engineer to state anything like this. How do YOU or I know what level of learning anyone here has had?

And, if you're here to teach, then DO SO. Without the arrogant garbage.. I'm sure that all who read your postings here will be sure to recognise your importance...;}