I think this must have always been a concern for companies like Sendgrid. As someone who operates a service to allow incoming email (CloudMailin) there's nothing more worrying than the big boys coming along an sweeping you up. However, so long as you continue to add value people will choose your product over the competition. Moves like this can ultimately lead to a far better product in the long run.
Having tried the service it's currently clunky and command line based too! I wouldn't actually call these comparable products. SES seems more like it replaces transactional emails that users might have previously event sent without a lot of a anti-spam measures. The value that companies like Sendgrid/Mailchimp/Postmark add outweighs the price for me and, at least, in the short term I won't be moving anywhere.
Having tried the service it's currently clunky and command line based too! I wouldn't actually call these comparable products. SES seems more like it replaces transactional emails that users might have previously event sent without a lot of a anti-spam measures. The value that companies like Sendgrid/Mailchimp/Postmark add outweighs the price for me and, at least, in the short term I won't be moving anywhere.