Got this a while ago while saving a bunch of links for my blog; unfortunately the email address did not respond for information
Too Many Requests
We are limiting the number of URLs you can submit to be Archived to the Wayback Machine, using the Save Page Now features, to no more than 15 per minute.
If you submit more than that we will block Save Page Now requests from your IP number for one day.
Please feel free to write to us at info@archive.org if you have questions about this. Please include your IP address and any URLs in the email so we can provide you with better service.
I wish there was a queue service that would make you wait longer, but does fulfill the request.
–jeroen