Its social web services initiatives have been patchy at best, so Google hasn't managed to muscle in on Facebook or Twitter like it has with Microsoft and Yahoo.
The writer probably means to say that the quality of Google social web services has been inconsistent, tending to poor.
I doubt they are referring to coverage (another possible interpretation of patchy) since by that measure any service provider, including Facebook and Twitter, would also fall short, making the comparison pointless.
Interestingly, Etymonline has patchy as derived from the second definition of patch below.
patch (1) "piece of cloth used to mend another material," late 14c., of obscure origin, perhaps a variant of pece, pieche, from O.N.Fr. pieche (see piece), or from an unrecorded O.E. word. The verb is mid-15c., from the noun; electronics sense of "to connect temporarily" is attested from 1923. Phrase not a patch on "nowhere near as good as" is from 1860.
patch (2) "fool, clown," 1540s, perhaps from It. pazzo "fool," which is possibly from O.H.G. barzjan "to rave." Form perhaps influenced by folk etymology derivation from patch (1), on notion of a fool's patched garb. But Buck says pazzo is originally euphemistic, and from L. patiens "suffering," in medical use, "the patient."
patchy 1798, from patch + -y (2).
And NOAD on the phrase at best (coincidentally using patchy as well):
at best taking the most optimistic or favorable view : signs of recovery are patchy at best.
It's sometimes used in parallel with at worst:
at worst (or the worst) in the most serious case : at worst the injury could mean months in the hospital. • under the most unfavorable interpretation : the cabinet's reaction to the crisis was at best ineffective and at worst irresponsible.