I generally don't bother, because it's just more security risks.
I generally don't bother, because it's just more security risks.
If you check a username, then you would probably also be revealing the IP address range and browser referrer that is normally used to access your account.
Google uses IP address and location to help detect illegal access. So giving away this information could make it easier for your account to be stolen.
He might even be able to use the same IP as you, if you happen to be using a gateway with many machines behind it, and one of them is compromised.
Let's do some quick back-of-the-envelope math. 5M addresses, with very few longer than 25 characters. Let's say the average is around 17 characters. 17 * 5 * 10^6 = 35 * 10 ^7 = 3.5 * 10^8 bytes, or 350MB. Text generally compresses to 1/8 space with zlib, so the amount to transfer would be about 44MB, at most. Serving the list as xz compressed file could probably cut the size down to below 40MB.
In the age of 100MB youtube videos, that doesn't sound like much to me.
http://arstechnica.com/security/2012/12/how-script-kiddies-c...
http://arstechnica.com/security/2012/12/how-script-kiddies-c...