The word vouch has been used many times in the forum and real life and the meaning remains inconsistent because the word has to be taken within the context of the situation and conversation. You can vouch for someone on the basis you will become a guarantor if they default on a loan whilst it is also to vouch for someone that you will not become a guarantor if they default on a loan.

I have seen members vouch for campaign managers when companies have created threads looking for someone to handle their forum signature campaigns but none of those members would volunteer to pay even $1 from their own pocket if the campaign manager ran off with the escrowed funds. When they made the vouch they knew they would not cover any potential losses from their own pocket but it still did not stop them from vouching.

The word has been used a lot without but it can only be used correctly if the one vouching states explicitly what he is going to do/not do in the event his vouching of another person leads to a problem.