It's likely that a normal Gmail users didn't notice that Gmail has a lot of limitations for sending messages. Here are some of them, as mentioned in a mail from Google:
- 500 messages per day (i.e., you can hit 'Send' a maximum of 500 times)
- 500 unique recipients per message
- 2000 total emails per day (for example, you could send one message to a group of 500 people four times)
In addition to these limitations, "Google will temporarily disable your account if you send a message to more than 500 recipients or if you send a large number of undeliverable messages". According to the help center, you can only send a message to up to 100 people at a time if you use POP or IMAP.
Google explains that these restrictions were created to fight against spam and to prevent abuse. The same rules are enforced for Google Apps users, as well.
Om Malik thinks that "500 messages are nothing in this day and age, especially if you are in the information business as I am" and wonders why Google doesn't list all these restrictions.