I'm not sure if my mouse is broken because clicks aren't registering or if I'm just... not hitting things, or there's some other problem? I've been noticing this for a couple of days now. But whenever I deliberately test clicking everything seems fine. 
Update on the mouse: it's definitely broken. The left button is only registering about 50% of clicks now, and it's been driving me crazy. This mouse lasted just barely two years. Time to get a new one, again... 
@kianga Geez, how strong IS your finger!?
@ZeirosLion It's getting stronger because I need to press down real hard to get my clicks to register 
@kianga I had the same problem only my mouse button broke in two pieces a little bit later.

@Nightraccoon Broke in two!  

Mine usually seem to die in more subtle ways.

@kianga I've had a lot of reliability trouble with keyboards and mice in last few years. My significant other even more so as she uses gaming mice with extra buttons, which really restricts selection, especially with ergonomics in mind.
@PlasmaGryphon Yeah, this is happening way too regularly for my taste. I've tried almost every brand and they all seem equally unreliable (and unrepairable).
@kianga
I have noticed this to - which is why I'm looking at the ploopy mouse or something similar for my next one. I want something I can replace parts on or modify to my needs.
@PlasmaGryphon

@bel @PlasmaGryphon Oh, that's an interesting project - I'm saving that for the future, thank you!

But yeah, it seems so wasteful. That broken switch probably costs a few cents and everything else about the mouse is still in perfect condition.