Question: could services like welfare or food stamps still be effective if they were donation based instead of part of mandatory taxes?

They would be more effective. Unlike the government, private services have a strong incentive to make people on charity self sufficient and self reliant to the greatest extent possible. Even if they can't carry 100% of the load, a lot more effort would be put into making them self reliant and self sufficient. Also, private charities weed out the scruff. Charity would be conditional on things like not using drugs, and making a good faith effort to improve your life, rather than an entitlement.

Finally, when people are not taxed and regulated, that frees up a ton of capital. In fact, I would argue that most people on government assistance could support themselves if the state would just get the fuck out of the way. For the rest, supporting by charity would be easy.

/r/Libertarian Thread