I certainly wouldn't be able to! As Vaith said, it could be done if one creates short posts, but those posts will probably lack substance.
There are however instances where someone might post up to 10 times or more per day and still create relative and informative posts. One such example might be someone blogging about up-to-date cryptocurrency/stock trends. As the the values in this area are constantly changing, it is necessary to post frequently. This doesn't usually take as long as creating original content, as they make use of a template and only adjust only certain areas, apart from writing their analysis
So yes, for the average blogger 10 posts would be quite a lot! It's better to create fewer posts that actually bring value to the community. People following you would also enjoy your posts more if they don't feel like their being bombarded.
You can post as many times as you want but there's an unwritten rule that no one talks about, which says you have to respect others and not spam the blockchain. Quality is what makes you better and respected, not quantity.
Before HF20 was implemented, I've seen users posting literally ten times a day, mostly prayers and quotes, which, let's admit, wasn't their own content. These people have disappeared after HF20, which is a good thing.
Back to your question, let's analyze what posting ten times a day means. Creating a quality post needs time, which we all know it's limited. Even if you have nothing else to do, just post on Steemit all day, you'll end up hating it after a few days, not to mention you're going to run out of subjects in no time. No matter how good you are, i don't think you can keep up.
Your followers are going to unfollow you because they will be fed up with you pretty soon and you don't want that, because without followers what's the use of posting ten times a day?
Some do post 10 times a day and upvote their posts. I couldn't do it as firstly what would I write about?
I post 2 times a day and that is hard enough to keep up. Finding another 8 posts would be impossible for me unless I took photographs etc. I work as well so 10 posts a day would be doing Steem full time and even then I just wouldn't cope.
There is a limit to how many posts your followers will upvote and doing 10 is similar to spamming. I know some who do 5 a day and is hectic for them. My maximum is 2 and even then I don't do 2 a day everyday.
No way I would be able to create ten valuable post on a single day. I can barely manage two! I do however think people that post very short blog posts could manage ten posts, but these would probably not be as good as the blogs of the people that spend more time on each post.