There is a related practice where you can switch your current account. At least in the UK, there are several banks that will pay you from £100 to £150 for switching your current account to them. Like the above practice of churning, this will have a small negative impact on your credit score in the short term, but is otherwise fine. The bank will do all the switching for you, and transfer all your direct debits, standing orders, etc, from the old account. Once you have received the switching bonus (normally within a month of the switch), you can then always switch back. Naturally, you should choose a no-fee current account to switch to (all of these offers allow that). Note that some of these switching bonuses require you to have at least two Direct Debits and pay in a certain sum of money per month, so read the fine print.

The following offers are currently available in the UK (not necessarily an exhaustive list):

• Clydesdale Bank - £150
• Yorkshire Bank - £150 (but this is the sister bank of Clydesdale, don't think you can get both bonuses)
• First Direct - £125
• Co-operative Bank - £100, plus £25 donation to one of seven chosen charities (none really Effective Altruism, sadly)
• Halifax - £100
• M&S Bank - £100 gift card at M&S (£125 if you click through from the right feeder websites)

What you do with the money is of course up to you, but this is compatible with effective altruism. I have taken advantage of all of these offers at one time or another, and heartily recommend it.

EDITED TO ADD: Many of these bonuses cannot be claimed if you have already received the bonus too recently. So it's not like you can make £600 a month doing this!