Many modern web applications have a lot of spam deterrent such as Captcha, Bayesian filters, URL, ip detections etc. One example is trying to do 2 consecutive search on the CiviCRM.org forum and you will get a an error that look like
"Your last search was less than 5 seconds ago. Please try again later."
The concept behind this is flood control is to prevent a webbot (automated script) that is trying to spam and flood the server.
When I first started to use CiviCRM, because of all the functionalities and features. Often overlooked is the fact that there's no confirmation email option for users who completes a profile form.
A confirmation email in this case help reinforce the relationship between the organization and its users. As I understand this feature has been sought before and perhaps it is time to bring into CiviCore?
A couple month ago I raised the question about CiviCRM importing scalability, and received mixed answers.
CiviCRM should be mostly used for data import, not for data cleaning. Most importing scalability issues stem from people's reliance on the system to perform both data clean up and import. CiviCRM has a great data cleaning process that should be taken advantage of when doing a large import.