Corporate Defector seems to have three things going for it:
- It's free in terms of credits and influence.
- It sometimes gives you a bit of information about the corp's strategy. Put otherwise: it makes click-drawing for the corp more dangerous in addition to being efficient because it could reveal an agenda or trap to the runner.
- The Price of Freedom.
It has two major downsides:
- Opportunity cost (you could have slotted a different card).
- MCA Informant.
The problem with the defector is that the effect, while useful, is unreliable. If the corp doesn't need to draw extra cards or doesn't want to risk drawing extra cards or has an alternative way of drawing cards the defector is useless.
In general there are too few deck slots in a minimum size deck to justify cards that may be useful unless they're extremely useful (i.e. silver bullets like Plascrete Carapace). That leaves the defector without a ride.