To be honest, it hasn't been too common with me. It's only happened a couple of times and it's pretty much come down to obvious differences between the girl and I.
If it's a common occurrence, I'd have a look at what you're saying/how you're saying it, because based on what you've said they seem keen initially.
It could be as random as not using emoticons to convey tone through a difficult to analyse medium, or as blatantly obvious as you asking her to marry you/stick her finger in your bum.
Since I have become single it's been a common theme.
They have all been super keen at first, but then just start ignoring me.
I've had a couple be honest and say that they're aren't interested any more or what not, which is fine, but plain ignoring someone is just rude.
How long does everyone think is too long to wait for a reply from someone?
The above mentioned girl was a notorious poor texter, and regularly took a day or to reply to texts. Claims she was super busy with uni or what not.
How long is too long before the alarm bells start ringing?