I'd echo the other comments about pricing. It seems quite expensive given what you are providing. For example, I looked up the Google App Engine pricing for se

I'd echo the other comments about pricing. It seems quite expensive given what you are providing. For example, I looked up the Google App Engine pricing for sending emails and it's $0.0001 for each email. Additionally, it's unclear to me how your system handles things like bad emails, twitter being down, etc. From a custom standpoint, handling the messaging exceptions is nearly as important as actually sending the messages.