Over a sufficiently large timescale, I think is an inevitable scenario. However, I have no idea whether that large timescale is measured in decades, centuries or millennia. If it's the latter, then it's probably not a huge problem.

As long as a single bitcoin exists, there'll still be more fractional bitcoins available to divide among people than there are US cents*

* may not be precisely true, but it's something along those lines.

This is off by at least three orders of magnitude.

1BTC = 10M satoshi.

2012 US Penny Production = ~6B

6bn/10M = 600

Total number of us pennies made in the last 10 years tops 43B which pushes the difference from 600x to 4300x

1 BTC = 100M satoshi, not 10M

Shish2k's point stands, only with "430 BTC is as many satoshis as there are US pennies".

But this is irrelevant anyway. If 1 satoshi ever becomes too coarse-grained, the whole Bitcoin community would obviously agree to revise the protocol to further subdivide satoshis...

1 satoshi is classified as "the smallest denomination currently possible".

The important part of that is "currently possible". The protocol allows for us to divide down as far as we want. All we need is a software update.

Even if there were an upper limit of 21 trillion bitcoins, people would still be worring about them being lost, even though it makes no difference.