I'm a pretty ruthless blog un-subscriber. It's nothing personal, I just want to save my energy for blogs I care about. I'm constantly browsing around and picking up interesting looking blogs, but to make it into my long-term reading rotation, you have to make through several rounds of cuts.
1) You don't motivate me to want to comment
Whenever a post catches my eye long enough for me to A) finish reading the post, and B) actually comment on it, I will flag that post in Google Reader with a star. About once a month, I scan back through my subscriptions and see which ones have more "marked as read"s than stars and I unsubscribe to those. Basically what it comes down to is... if I scan through more of your posts than I read... I'm moving on.
2) Your feeds are cluttered with ads or truncated off
Especially on newly-subscribed-to blogs, if I'm reading through a feed and there are ads in it or if the feeds are truncated... I unsubscribe on principle. I won't support bloggers who purposefully make it difficult on their readers to read their blogs. End of story.
3) You post way too often or not often enough
Posting too often or not enough gets you on the "Probably Will Cut Soon" list. You might make it out alive if you get on that list, but probably not. Let me explain...
If it's been a month since I've had time to read your blog and you STILL haven't posted anything new... you're not posting enough. On the other hand, if I come around and you've posted 60 posts in that time... you're posting way too much.
Most blogs kind of fall into a happy middle ground, but just be cognizant of your posting frequency, that's all I'm saying. I tend to find blogs most pleasing when they post 4-7 times a week. Less than that and it's hard to get a feel for what they're about. More than that and I feel like they're spamming me.
4) Your posts are generic and not specific to you
Another thing that will get you on the "Probably Will Cut Soon" list is if you only post generic posts. What qualifies as generic? Photo posts, "what I wore today" posts, "here are my lovely sponsors" posts, blog hops, giveaways, Pinterest finds. Don't get me wrong, these are important things... just not every day.
I'd rather hear a funny story about how you dropped eggshells in your omelet this morning. I want to know what makes you you. Then when you share your favorite Etsy finds, I'll care. However, if ALL you ever show me are your favorite Etsy finds... I'm moving on.
That being said, there's a reason behind my madness. I'm not cutting to be mean or to say that anyone's a bad blogger. A lot of times it just boils down to personality; we're interested in different things or whatever. But honestly, the main reason I cut so many blogs is so that the ones that I keep are the ones that inspire me, motivate me, and move me to build friendships with those bloggers. Because really, isn't that the whole point behind blogging in the first place?