I'm afraid a lot of the problems that come up might be best dealt with by the individual host. Circumstances are different in each case. If someone has joined a swap but doesn't seem to be "present", that would have bearing on what would be done if they didn't get their seeds in on time. I wouldn't feel bad about just telling them "sorry you missed the ship out". On the the other hand if someone is participating but for some reason is a little late on shipping, well it's a judgement call. I'm afraid paying ahead of time might be more hassle than it's worth.
Weedwhacker - I love the missing package story. I've gone over to the neighbors two days in a row now, they are out of town and my new greenhouse cover is late arriving. I keep thinking it's got to be sitting over in their yard somewhere.
