I agree. I've seen entire threads here debate what should be considered savings. The article suggests we should have six months worth of expenses saved and readily available.
For many American's that's probably good advice but for many others this would constitute tying up a very large sum of money. That I should forego a 10% average return for a 2.5% return, just so I can be ready for unforeseen circumstances, doesn't seem like the best advice to me. I can always borrow from my 401(k), or from any number of zero percent or low percent credit cards, to meet for unplanned issues. Personally, I would rather do that than lose the opportunity to earn an additional 7.5% on six months worth of expenses. That would add up significantly over the years.
I guess it depends in part on how many dollars we're talking about. Personally, I think of emergency money as just that: emergency money. I don't fret about getting a return on it, because that's not what it's for. To me, I'd be very sorry if I put the money into stocks or whatever, and then had an emergency come up. So I do both: I save for emergencies, AND I invest and get as good a return as I can. And anyway, don't most people hedge a bit anyway? Why not think of your emergency savings as a hedge? For me, it doesn't constitute a huge sum of money, and whatever I lose in interest or gain is worth it for the security it brings. Call the difference between 2.9% and 7% earnings an insurance payment to myself.