mayer is correct.
According to Apple, the Mac Mini 2011 supports '[http://support.apple.com/kb/ht4805|1 GB, 2 GB, or 4 GB in each slot]' which would max total of 8GB.
However, all of the Intel CPUs used in the Mac Mini 2011 contain the RAM controllers:
[http://ark.intel.com/products/52224|i5-2415M] (2.3 GHz Dual Core)
[http://ark.intel.com/products/52229|i5-2520M] (2.5 GHz Dual Core)
[http://ark.intel.com/products/52231|i7-2620M] (2.7 GHz Dual Core)
[http://ark.intel.com/products/53463|i7-2635QM] (2 GHz Quad Core)
And all of these CPUs max at 16 GB of supported RAM.
This has been [http://blog.macsales.com/11292-owc-announces-industry%E2%80%99s-first-16gb-ram-upgrade-for-latest-apple-mac-mini-models|confirmed] by [http://www.corsair.com/en-us/memory/mac-memory?memorysize=16GB%20(2%20x%208GB)|several places], and 16GB is what I use in my 2.7GHz Mac Mini 2011.