In all honesty, a data node should be visible with or without the goggles.
The difference is that without goggles, they are just small distortions, or a cloud, or some random "glitch" that just doesn't make any sence there. Pop on the goggles, and bam, you see the rift in the code. The goggles also let you see the nature of the glitch so that you can exploit it with your tapping tools.
Think along the lines of the Animatrix short with the freaky "haunted" house.
The nodes should spawn in areas that are "stressed" or unusual in the first place. Create a predictable locations that are hard to get out of. This way the risks get higher, and the rewards can get beefed up to something at least somewhat reasonable.