The lightning network backend is still in beta and the network is constantly growing and changing. There could be bugs and sometimes there is not enough liquidity in the channels.
We do our best to monitor and take proactive measures. If something doesn't work, try again later. Use this service at your own risk.
We currently impose a soft limit of 0.10000000 per key.
A key is needed to make sure that if you make a payment and it takes time, it will end up in the right place eventually. Also it is needed so you have some way to withdraw your satoshis.
The private key is kept on a cookie in your browser. It is wise to write it down in case your browser forgets the cookie.