The documentation is not clear, how MaxBytesPerRead is different from other limits, e.g. MaxBufferSize or MaxReceivedMessageSize.

From http://geeksdiary.com/archive/2007/05/23/pox-streaming.aspx :

The MaxBytesPerRead value indicates how many bytes the XmlDictionaryReader should read when reading the element start tag and its attributes. Therefore, this value should essentially be large enough to read that information. If you set an unnecessarily large value here, the XmlDictionaryReader.Read() method will not return until it receives enough bytes from the underlying transport(this could be problematic if you receive very small data chunks with a considerable amount of delay)

The XML Config shown has a simple bug that might be anoying if you copy paste into a notepad with existing data...
<readerQuotas
maxArrayLength="Integer"
maxBytesPerRead="Integer"
maxDepth="Integer"
maxNameTableCharCount="Integer"
maxStringContentLength=="Integer" />

maxStringContentLength has to equal signs where it should only have one!

So that the search engines can index this page (which is the answer), here's the common message given when MaxStringContentLength is too small.

The formatter threw an exception while trying to deserialize the message: Error in deserializing body of request message for operation 'something'. The maximum string content length quota (8192) has been exceeded while reading XML data. This quota may be increased by changing the MaxStringContentLength property on the XmlDictionaryReaderQuotas object used when creating the XML reader. Line 1, position 8815.