The fee should be automatically inputted, or there be at least an option to auto-fill in the correct fee. It's a minor annoyance that you have to manually put it in and it would definitely stop things like this from happening. New users also often don't really know how much to correctly send.

Indeed it is not only blockchain.info. I have heard of people accidentally mistyped the fee amount in Electrum as well.
IMHO, all wallet clients should warn the user when the fee amount is too big, say 10x more than min fee.

The problem is that bitcoin tx fee depends on the tx size in KB.
To calculate the "correct fee", you will need to know the number of inputs and outputs of that tx, which is a bit too difficulty to those new users...

There is still a problem in it, as people usually don't "consolidate" their bitcoin.
So, the sender may have used 20 different addresses to receive bitcoin before (say, 10 addresses for 10 different faucets, 1 for sig ad payment, 1 for selling domain, 8 change addresses, etc).

I am afraid It will be too difficulty to use then.