Scan this, Chummers.
Imagine your runner team has both a Technomancer and a Decker. They decide to work together to hack a server (two jacked-in hot-simmed heads are better than one, right?). In order to not arouse suspicion as they enter the host, they both switch to silent running (-2 to matrix actions, but oh so sneaky). They enter the host and both make a Matrix perception test to find the paydata they want to steal. One finds it, the other doesn't.
The patrol IC is sitting quietly because it has no reason yet to suspect that there are icons running silently inside the host.
Now, here's the problem - if one silent-running hacker wants to let the other silent-running hacker know where the file is, how does he/she? Can they see each other? Do they have to Matrix Perception to find each other? Or can they just use the "Send Message" action to let the other know exactly where the file is?