What are those visits from appspot.com?

I have a new wordpress site upgraded recently. Then I noticed there are very frequent visits from appspot.com:

Last referrers

May 26, 2009 16:26:33 http://16p0479z.appspot.com/
May 26, 2009 16:26:31 http://mybandjoun.appspot.com/
May 26, 2009 16:26:28 http://admitguru.appspot.com/
May 26, 2009 16:26:17 http://admitguru.appspot.com/
May 26, 2009 16:25:54 http://16p0479z.appspot.com/

I know appspot.com is a google apps platform. But what are those subdomains? Their names look spammers. What's their purpose of visiting? That is just a typical business site with no secret content.

Is there a way to block them from wordpress? :rain: