There are numerous add-ons for Joomla to suit any type of website. There are open-source add-ons and there are commercial ones. There are hacks to modify some functionalities. It is a pity however that implementing a hack means obliterating the code and could lso be a possible source of security breach.
One such feature that I always wanted to be a part of the Joomla core is the CAPTCHA. There are numerous CAPTCHA add-ons listed on the Joomla download site but thay are all hacks which requires editing the orignal Joomla core to implement.
Another problem with hacks in Joomla is the possiblity of over-writing the modiied code when upgrading to the current version.
The use of CAPTCHA is very important for site which hav user registrations. I stopped user registration in my site TFE to stop spams as I am getting several spam registrations everyday. After three months when I open up registation again, in just a couple of hours, I already got two (2) spam registrations. That's how nasty spammers are.