Not only wpmu, wordpress Standard also has the spam registation problem.. especially with buddypress.
@m@rk I know SI captcha work with buddypress. I created a test installation and tried, its works there.. but when i tried in another shared hosting package of same server, it doesn’t. I dont know the reason. The image is not get displayed….
I read that article. At the end of it, there is a suggestion for using Invisible-defender plugin modified for buddypress. I tried that plugin, but it shows error when a registered user try to login. The plugin available at wordpress plugin site is not for buddypress i think.. Anyway i installed the latest from wordpress plugin site. Let me wait and check whether it block spam registration.
I tried captcha technique. but some how its not working with my installation. I dont know what the exact reason is. The image is not get displayed. when i clicked on the test link at the Si Captcha settings page, it is redirected to “not found page” ..
But Buddypress test site (testbp.org) does not hold a captcha.. but still it seems that there is not much spam registration. How they control spams without using captcha. Any idea about it?..