[SAI_Peregrinus]

Bacteria are the biggest argument against grey goo. They already are, they already exist, and they're already everywhere, yet things other than bacteria still exist. They've had several billion years of evolution to work on it too.

They're probably in local maxima, not in any global maximum, but it's also likely that there is no single global maximum given how different the requirements are for using different energy sources.

[Symmetry]

The thing I would worry about it replicators that use stronger chemical bonds than bacteria do and can eat bacteria but can't be eaten by bacteria. They would probably have to reproduce much more slowly due to higher energy requirements but if they end up eating everything in the long run it might not matter.

[DagAgren]

If using stronger chemical bonds was advantageous, bacteria probably would be doing it already.

The weak bonds is what complex chemistry and thus complex functionality possible. Stronger bonds is dead matter, and dead matter does not compete.

[philipkglass]

Incorporating fluorine in a molecule offers additional flexibility over the more common chlorine and bromine compounds commonly found in natural products. For example, the fluoroquinolone antibiotics are distinguished by their introduction of fluorine, yielding compounds more effective than found in nature.

There are a few fluorinated natural products made by wild organisms, but they are very rare considering the elemental abundance of fluorine on Earth and the high utility found for fluorine in pharmaceutical development:

https://www.ncbi.nlm.nih.gov/pubmed/23034231

The strong bonds formed by fluorine, and its formation of insoluble compounds with alkaline earth metals, probably explains the rarity of natural fluorinated products. The fluorinated natural products are no more "dead matter" than other poisons evolved by plants against herbivores, but it's hard to evolve out of local minima that exclude fluorinated compounds.

[carapace]

I suspect that multi-cellular life is the art form of unicellular life.

We are art made by microbes. (I like to think.)

[gHosts]

Arguably you're just a great big pile of grey goo.

ie. It's not an argument against grey goo, it's an argument the grey goo catastrophe rules everywhere and has done so for eons.