The above use of sub domains isnt a black hat technique, its been going on for a very long time with some major authority sites. If you are generating content from an "auto loader" that maybe a spammy techinque and if your are duplicating that content from sub to sub....thats a very bad idea. You can effectively use that setup, BUT, be very carefully in cross linking sub to sub that will get you banned for link spamming
Cheers
WEB_I
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Online Guerilla Marketing