I am sure everybody specially regular bloggers are sick of deleting and marking spam those Viagra comments and other spam comments, which are waste of time.
Every morning you check your admin email of your blog , you see 4 out of 5 comments which are absolutely spams.
These spam comments are posted via scripts running like robots or bots, which can easily see an open input form and fill it with Junk data. The problem is identifying whether it is filled by a Human or a Script?
S0me dude way back in 2000 has already addressed this by introducing Verification Code method within every form. CAPTCHA official site makes it easier for non programmers and non techy users to implement this small script concept, which ensures that only and only a Human can fill the form/comment box etc.
You can download wordpress plugin and say goodbye to all spammers 