And what if the value of bitcoin drops because of some speculations? You will lose that money. The bitcoin can't be taken seriously when it comes to commerce. I don't think anybody would agree to sell a product lower than it's value to get some coins, if you want coins you can simply buy it with money.
If I had a widget or a service that I wanted to sell, I'd offer at least a 5% discount for BTC, and probably more like 15% or 20% just to avoid the hassles of acquiring BTC in other ways. As it is I've got about the number of BTC that I want, nothing I want to sell, and there does not exist a means by which low-ish value transactions can be performed safely and inexpensively anyway (imo.)
You are of course right about the volatility, though it can work in two directions. That is in fact a big part of the reason I am interested in holding BTC. This speculative use-case is not appropriate for typical commerce though so I'll largely agree with your point here. I don't think it dooms Bitcoin to a value-less state, and it could even work in the other direction in terms of values against other stores.