Pipe drips water on my exterior porch?
I would bet against this being the regular drain for the air conditioner/furnace.  The A/C creates a lot of water, and only the most inept remodeler would allow that to drain on a finished porch like that.

I had almost the same situation in a house and the dripping pipe came from the water heater's temperature/pressure relief valve and that had to be replaced ($20, not bad).  The other option would be that it is from the A/C but its the secondary "overflow" drain that drips when the main drain is clogged.  These are sometimes placed in visible areas so that you can see them dripping.

To answer your last question, I would assume that yes, dripping from such a conspicuously placed pipe does indicate a problem that should be addressed.