2004 Camry LE - Should I Be Concerned About Squeaky Brakes?

Now, brakes usually squeal when you step on the pedal, not when you release them. Besides the simpler issues (embedded dirt, worn pads, old brake fluid, old caliper rubber parts etc), the fact that they make noise after you let off makes me wonder if it's the wheel bearings acting up.

Because one known way to quiet a wheel bearing during diagnosis is to lightly step on the brakes.

A little google shows:

"Brakes squeal or rattle" can be caused by:

"a) Wrong type of pads/liners b) Dirty floating caliper recesses c) Spring force insufficient d) Brake disk not aligned with first caliper e) Brake-disk run-out f) Excessive thickness deviation within braking surface g) Brake drums eccentric h) Knocking brake drums i) Dirt and dust in brake drums j) Liner wear excessive or one-sided k) Rust edges on brake disks l) Pad loose m) Wheel bearing play excessive"

When a used car dealer replaces anything on a car (tires, batteries, brake pads, etc) they get the cheapest ones possible, and usually not the OEM parts (even if you buy a certified used car from a new car dealer).