Until and unless, the barriers to entry are very strong enough, a zero-RM cost business turns out to be a bad business in the end.
Think about it, hydel energy is a zero RM business....but it has such strong barriers to entry that companies into it will continue to demand very decent P/E. Telecom's strength was that its running cost in comparision to its revenue streams used to be pretty negligible. But, with increasing competition, increased ad spends and network expansion costs keeps the running cost high whereas the revenue streams may start to shrink. Increasing costs and falling revnues, in short, is the bane of this industry.