Some blogs do expect free things to review. I review products on my blog, but I never ask people. I figure - and this goes for people who have asked me, too - that if I want to review something, I will buy it. Instead, I let people come to me, and ask to be reviewed.
A lot of bloggers expect to be able to keep the item they're reviewing. I leave it to the seller to decide that. A lot of bloggers see it as a form of payment, but that is NOT what it is supposed to be at all, and some sellers see letting bloggers keep the item as a way to ensure a positive review.
Not all bloggers expect to keep the products, and not all bloggers will give a shining review just because of a freebie.
If I were you, I'd decline the ones that ask right out for a freebie. A lot of bloggers go into product reviewing purely to get free stuff. It's hard to know who is legit and who isn't, as well, because followers and stats mean nothing. Just because someone has 6k followers, doesn't mean they won't try to screw you over.
You would be better off approaching blogs yourself. Some bloggers who ask may just want your stuff, and their blog and readers may not be suited to your products, so it would just be a waste of time for you.
If you decide you want your products reviewed, it's easy enough to hunt down blogs that are suitable.
Of course, this isn't to say that NO ONE who asks you directly can be trusted, at least some people have come right out and stated that they want an item for free. You could take that as honesty, or you could take it as stupidity.
Follow your gut. If you think it's worth risking a single product, then do it. It could be worth while. But research the blog - read what they blog about, and have a look at other product reviews they've done, and get an idea of that.