In our org, we don't want any Marketo pages indexed. Thanks to Sanford Whiteman this helped us overwrite all page Robots to be "no index, no follow". http://blog.teknkl.com/customizing-the-robots-txt-for-marketo-lps/?marketo-nation
God I wish I knew about this a few days ago...
Ha, forgot to suggest my other idea!
Out of curiosity, does that happen even if the robots line is above it?
Yeah, every time I tested it it was well before the offending '&' (and before any of the marketo meta tags).