Everyone has a different opinion of how much gold is 'enough' gold. I tend to hang out with players that are pretty big on min-maxing, the people that are always prepared, so my sense of what's 'enough' is a bit inflated. I'm sitting on roughly 10,000 gold right now, and I only recently started feeling like it was 'enough.' I'll be hemorrhaging gold at level 80 leveling professions and getting my gear up to par, so I'm sure most of that will be gone in no time. I could also get the gold very, very easily once I've hit level 80, and not have any issues. I just had that urge to be extra prepared that wasn't sated until I hit 5 digits. It actually wasn't too hard to get. I just farmed herbs here and there, and it just sort of accumulated.
How much gold do you think is enough gold, especially when we're heading into an expansion? Are you content to sit down in the single digits, and go out and run a daily quest if you need to repair your armor? Do you gather up as much gold as possible and sit on it?