I agree with gameutopia that blocking IP and bots via htaccess is not the way forward as there are plenty of software available which will enable spamers to rotate their IP. Therefore, htaccess is only a temporary solution.

A lot of spammers are able to create fake accounts simply because a Join in page is either standard by default or too simple. If you are running a professional website and care about your members that I suggest the following

1. Make your Join in page unique - add more see more fields that are relevant to your business. In textarea, for example, put a limit on how many characters have to be inputed to proceed to the next field.

2. Get members to confirm the validity of their email account upon registration i.e. they must mannualy click on a link within registration email to complete the registration.

3. Authorise membership manually only once you have checked their profile. It's a tedious task, but eventually you will build a good database of members.

4. Also, you may ask your members to pay a symbolic 1 USD to complete the registration by Paypal for example - to make sure they are not bots.