Boy, that escalated quickly... I only wanted an answer to something that seemed counter intuitive.
I constructed a test sketch that turns 3 LEDs on in off in every possible combination, using a separate 200 ohm resistor for each cathode (I have lots of those!) LED brightness never changed.
I then tried using a single 1k Ohm resistor and 2 200 ohm resistors in series tied commonly to each cathode. Each turned on fine, but I could not turn on all 3 at the same time. Too much current, I guess.
I'm going to spring for some 1k resistors (I know, my maker shopping list is quite long right now...), but I find it strange that it worked with the ArduinoISP sketch, but not this test sketch.
A note to Grumpy_Mike: I'd greatly appreciate it if you wouldn't try to "haze" me. I am not trying to "mislead beginners" and I don't deserve for anybody to "come down on me like a pile of bricks". Simple questions deserve simple answers, and I don't merit insult, even if perhaps my question is ridiculous.