The section of the video showing 'Scrolling' has 12 units daisy chained and working together. That's all the boards I have made up to date. At this stage I don't expect to be building up the remaining 8 spare PCB (I had 2 lots of 10 made up), but I can't see any issues arising from having more of the units connected. Any specific reason you see 10 as a limit?
I get my 8x8 matrices from eBay. The last lot I bought were from http://www.ebay.com.au/itm/230754163950?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649.
The controller chips come from Tayda Electronics http://www.taydaelectronics.com. They are about $1.25 each, so are probably not 'genuine' but seem to work perfectly well. Here is an interesting article about that http://tronixstuff.wordpress.com/2013/05/16/the-max7219-led-display-controller-real-or-fake/. I also get my passive components from Tayda.