[pzhon]

Some people find that they play significantly worse while multitabling, but still win more money per hour due to getting more hands.

If your win rate per hand drops, then you need to increase your bankroll requirements inversely. If your win rate does not drop, then you do not need to increase your bankroll requirements, any mroe than you would need to increase your bankroll requirements on a site that deals more hands per hour on each table.

The same is true when you move up. Using a fixed number of buy-ins at all levels is an assertion that your win rate is the same, whether you are playing NL $10 or NL $100. The consensus is that the higher stakes games are much tougher, and do not allow win rates nearly as high, which means you need more buy-ins to be as safe while playing NL $100 than you do to play NL $10. If you are so conservative that you think you need 20 buy-ins at NL $10, then you may need 60 buy-ins to have the same level of safety at NL $100 if your win rate is 1/3 as much.