Can too many electolyte supplements be dangerous?
Yes, too many electrolytes can do all sorts of bad things to you.

Good article here: http://www.livestrong.com/article/521763-can-you-consume-too-much-electrolytes/

The U.S. Army has done a lot of research, here's probably the most pertinent paper: http://www.ncbi.nlm.nih.gov/pubmed/10410838

In general, if you are mixing the drinks according to the directions, you won't be too wrong. Most will be a more natural mix if you mix according to directions then dilute 1:1 with water.

Happy Riding.