Agreed, though I think its also coupled with just a lack of understanding of what MongoDB does beyond just "its NoSQL!". So many people are used to working with RDBMS. They just seem to make incorrect assumptions about MongoDB based on what they thought were universal rules about databases.
Mongo's a tool. Its not right for all situations and it definitely has some maturing to go still, but its good to use in certain situations, provided you're properly informed about it.