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Recent high resolution spectroscopic analysis of nearby FGK stars suggeststhat a high C/O ratio of greater than 0.8, or even 1.0, is relatively common.Two published catalogs find C/O$>0.8$ in 25-30% of systems, and C/O$>1.0$ in$\sim$~6-10%. It has been suggested that in protoplanetary disks with C/O$>0.8$that the condensation pathways to refractory solids will differ from whatoccurred in our solar system, where C/O$=0.55$. The carbon-rich disks arecalculated to make carbon-dominated rocky planets, rather than oxygen-dominatedones. Here we suggest that the derived stellar C/O ratios are overestimated.One constraint on the frequency of high C/O is the relative paucity of carbondwarfs stars ($10^{-3}-10^{-5}$) found in large samples of low mass stars. Wesuggest reasons for this overestimation, including a high C/O ratio for thesolar atmosphere model used for differential abundance analysis, the treatmentof a Ni blend that affects the O abundance, and limitations of one-dimensionalLTE stellar atmosphere models. Furthermore, from the estimated errors on themeasured stellar C/O ratios, we find that the significance of the high C/O tailis weakened, with a true measured fraction of C/O$>0.8$ in 10-15% of stars, andC/O$>1.0$ in 1-5%, although these are still likely overestimates. We suggestthat infrared T-dwarf spectra could show how common high C/O is in the stellarneighborhood, as the chemistry and spectra of such objects would differcompared to those with solar-like abundances. While possible at C/O$>0.8$, weexpect that carbon-dominated rocky planets are rarer than others havesuggested.

On the Carbon-to-Oxygen Ratio Measurement in Nearby Sunlike Stars: Implications for Planet Formation and the Determination of Stellar Abundances