Summary: Negative aspects are easy "push button here" dispensers for Fate points, but spamming that button needlessly is boring at best.
Two things need to be kept in mind: drama, and the Fate point economy. Being stymied or drained of Fate points by the same problem over and over isn't dramatic or interesting, so don't do it. But the Fate points must flow! So here's how I approach compels in my games.
Most of the time, the Fate point economy should take care of itself. If aspects are interesting and natural to compel, players will often do it themselves! Frequently my job is simply noticing that their natural role-play choices deserve Fate points, and handing out the points accordingly.
If players aren't self-compelling a lot it may be because they feel too overwhelmed by the challenges I'm giving them, so they don't want to invite more obstacles. In that case, I need to back off and give them room to make problems for their characters.
More often, however, it's because our aspects weren't written so it's obvious and interesting to compel them. That means we need to revisit aspect-writing and revise our character sheets accordingly, but in the meantime aspects such as Steers like a cow are great filler to keep the Fate point economy afloat.
Look for compels when pools run low
When players start to run low they often cast about for opportunities to self-compel for more points. Obvious weak spots like Limited battery pack are a useful tool in these situations, especially when their character aspects might not be able to provide immediate traction for compels.
If a player’s pool runs low and they aren't self-compelling, it’s time to start looking for ways to feed them more points. Compels are a great way to do this because invoke points don’t go into the player’s pool until the end of the scene while compel points are usable immediately. This is where obvious but not overly dramatic compels, like "your gun jams," can be great.
Compel when the stakes are high
Drama, drama, drama. When nerves are taut and the stakes are high, throw out compels which will really gum up the works. This is a spice, not a protein, though: use it sparingly and its effect will be all the greater. "Your flashlight dies" isn't very dramatic--unless it dies just as you hear a spooky noise while exploring the sewers!