I'm with you that a lot of the side content is shit but to say that "literally" all of it is filler is just plain wrong. The secret agent and hidden camera ones were the main offenders but the other stuff was fine IMO. Showdowns were a great way to have multiple enemies zone in on your location and were a good test of skill (unless you came in with a full karma streak like I did sometimes). Audio files are fine in this day and age and some of the info locked in them was actually interesting so a minor pass can be given. Blast shards are the collectible of the day which usually is a useless distraction but tying it to upgrades and making them easy to spot on the map once you have control in the zone was a smart way to play that mechanic. Mobile commands are the same as showdowns but with you attacking instead of defending so same idea. And finally, regardless of your feelings on the matter because I know you'll disagree with me, the spray paint stuff was extremely clever and always a joy to do. All of the art was top notch and could be replicated in real life if you so chose and the control scheme for it was perfectly acceptable, even more so when you realize that you don't even need to hold the controller vertically after the initial shake if it really is too big of a hassle.
When it comes down to it, we got about 50% shit and 50% fun but the problem is that the shit is so bad that we feel like it ruined the experience.
Edit: Shit, double post. Sorry.
Everything in a game is a part of its score. Your post earlier about story: lol. Video games don't get a pass on the story department, if they are trying to tell a story then it needs to be a good one.