I'm allergic to Spam both types. The pork variety because I'm allergic to pork and the internet variety because it wastes my time. I am allergic to anything that wastes my time. My time is valuable and limited as it is for most of us. I get violently ill with both and yet I refuse to put any "I am not a robot" devices such as Captcha on my blog.
Wouldn't it be easier just add a Captcha? For whom? Me...probably, but not necessarily for my readers. Ease for my readers is everything. Captcha are hard enough for me to decipher with all the skewed letters and obscure photos of numbers, I can think of no other reason not to post a comment. I think I'd comment more if it wasn't for them.

approve comments it doesn't work so well. I'm the sort of blog reader that makes comments (sometimes). If I take the time to comment, I believe the commenter is owed a response. I actually go back to check if there is a response or click the email when comment is made box.
I understand if you are someone like Alex J. Cavanaugh who gets 100 + comments per blog post not answering each and every one, but my blog doesn't get the response his does. If it did I might take his tact on the subject. But I digress.
Spams are either complaints (negative) or flattery (positive). I have yet to see any of the spammers show up on my feed burner, although they promise they are following my blog. Maybe they have it bookmarked as a site where they can post their spam. I dunno. But I am vigilant. I take as much care of my blog as I do my other writing. It is my baby, my child that I'm sending out into the cold, hard world. Am I too attached to my blog? Probably. It's something I'm proud to say is mine.
Either way all spams ruffle your tail feathers. On any given post, the spam filter which catches bogus links will catch or I will delete, about ten emails. That amount may be irritating but I tend to look at the positive. That's only 3% of my total comments or emails I receive as a result of this blog or my books.

Yes, spams are a part of doing business on the web. There's no fighting it. Look at it from the positive point of view.
Did you know that spammers now have a way around the Captcha? They'll enlist the help of third world nations. They hire people who sit at the computer all day long who do nothing but copy and paste the same spam, and type in the Captcha.
For March of this year, I topped over 8,500 page views. No that's not cumulative but the figure for last month alone. Now if you take the 3%, that's a lot of spams in the month. To date, I've published 327 posts and received 325 comments. Yes, I've accounted for my replies to comments and subtracted them, and the spams in my spam folder are not counted. That's not too shoddy of a record. So if I have to go in a manually delete some spams from my blog...it's worth it.

What am I talking about...they don't actually read the blogs they are spamming.
Anyhow, keep writing and loving the Lord.