Can collectors garnishee money from a prepaid debit card?

You're using a technique that a lot of debtors use. Since you don't have an "account" it's not anything the creditors can levy on. They could garnish at your employer (if wage garnishment is practicable in your state) ... or they could call you in for a post-judgment deposition in aid of execution and you would be oath-bound to reveal that you were using a debit card. At that point they could go to the judge for a "turnover order" requiring you to give them some amount of money on a one-time (and perhaps even weekly) basis. But make no mistake, debit cards do create additional barriers for the collector--and where there are additional barriers, some collectors do simply pick up the next guy's file and go for lower-hanging fruit.

In Kansas, creditors are usually entitled to garnish your wages at the source (i.e. your employer). Thus, they would collected the garnishment before it ever hit your debit card. Wage garnishments are limited to 25% of your wages (again, usually). Beyond that, they might also be able to force you to turn over your debit card balance. That, however, would be very difficult since you could simply use the balance before they obtained a court order. Once the order was issued, you turn over the $5 or so left on the card, and then you replenish the card. They would have to get a new order, so on and so forth. Wouldn't make much sense--especially since they can simply garnish at the source. Bankruptcy could probably put a stop to the whole thing. Think about it.