For me, the maxim "If you see something, say something" is more than just for serious issues like a suspicious bag or someone who is doing something unsafe.
It's also for other things. For instance, if the climate control on a subway car is defective or if a bus is making a horrid noise. A transit system, whether it's a small town bus network or a system like New York City Transit (the MTA in New York), relies on riders for feedback for problems.
While the agencies like to stress security concerns (like suspicious riders and passenger activity), I expand that to include trivial comfort items, like a filthy subway car, bus, station platform, or any facility that might look out of order. It's our transit system, and as a result, we all need to be proactive in how we report problems.
Last week, during a subway ride in the city, I got on what was probably the filthiest subway car I'd ever seen. The floors and some seats were covered in some very nasty substance (which either looked like soda or coffee).
Regardless, I moved up two cars to avoid the substance and when I got off the train I notified a crewmember (and via social media, alerted the people at NYC Transit). I was notified a few days ago that the problem had been resolved (and I'm not surprised, as subway cars are supposed to be cleaned frequently).
We all know the cliche "it takes a village to raise a child." It also takes communities and active community members for a city to run-whether it's a small southern city likes the one my friends in Florence, SC live in or the second largest city in North America. When we're proactive, things happen.
The long moral of the story: always speak up, especially when it's necessary.