Honestly, as the person I am, I speak up more online than in real life, since in real life, I'm a quiet-ish person and keep myself to myself. It's just so much easier for me to be more vocal online because I have time to think what I wanna say, and I can delete/backspace stuff before it goes out to the other person or the online public - just in case I get in the wrong.

Absolutely depends on the situation.. lets give a few real life examples!
I work in a pharmacy that is probably the most busiest in the whole area... we have queues upto the door most days and as always customers get frustrated. When they are frustrated they take it out on us and other customers. As I see myself in a position of authority in the pharmacy over the customers I feel more inclined to speak up if they start having ago at another customer or one of my colleagues, no matter who they are I will speak up inside the workplace.

Outside of work I will most likely speak up to anyone apart from people who I see as being intimidating (group of people smoking 'plants') yh i value my life so i won't speak up then.

Stay down, give it some time, if the situation continues, speak up once and get all your points across, move on.