All that means from MSDN is that a random sample MAY be grouped. Its still a random sample.
Say you had 26 buckets - 1 for each letter of the alphabet - and they were filled with names and you wanted to choose a persons name randomly from one of those buckets.
Tablesample + NewID() would still get you a random person.
Tablesample would randomly get you one of the 26 letters and then newid() would get you a random person from that letter.
Seems as random as any other method.
sqlservercentral-1070393 (3/3/2010)
Mr Random again....tablesample limitations per msdn:
Rows on individual pages of the table are not correlated with other rows on the same page.
Never saw a database where that condition could be assumed. most are entered sequentially which is very likley to have correlations.
newid() and any function of it is "too perfect" the nice properties, such as good distribution of digits, has to be built in.
true random aren't so perfect exept in very large samples, and good psuedo random should be difficult to distinguish from true random.
If your doing a lottery, or a statistical study, definately look for better solutions.