WordPress MU

Since Mu will create a set of tables for each user when signing up, how many users can Mu's MySQL database support? For example, if 100,000 users sign up, there will inevitably be 1,000,000 tables in the databse. Thanks!

1700+ and no difference in performance at edublogs.org

Now, when IU get to 100k I'll let you know :D

capacity is limited by your operating system, not mysql. if you reach your os limit, simply create a new database, symlink the wordpress tables and alter the php code a bit. a 30 minute project for an intermediate coder.

Just one more question.
1) Use the same tables wordpress has and give each necessary table a userID attribute. Then modify the necessary queries inside PHP files to match the new database layout. Therefor, each table will grows very farst.
2) Use the way that MU currently used. Therefor, the number of tables will grows very farst.

Which way is better? (I believe that the author of wordpressMU must have a good reason to do it this way.)

the way it is currently used is better imho. if you put it all in one table, that table would get huge and would result in lots of waited table locks when doing updates, lots of full table scans when doing reads, and huge indexes.