No one has the time to download 10,000 books a day. If we're lucky an avid reader might nab a dozen a week, though it's doubtful they'll read them all. Personally, I download the top couple in the free list every once in a while, plus those I see advertised by twitter contacts. I haven't read even 1% of them.
Giving away books to find they don't get read is disheartening, but all the time they are on kindles they've got a chance of being read eventually. It still counts for Amazon's algorithms too.
The big problem is the effort to reward ratio. Being active on just twitter saps a good 20 minutes per day without trying. It can waste hours if you are prone to procrastination.
Maintaining twitter AND facebook AND google plus AND a blog AND pinterest etc etc etc... It's just not doable. Some cheat. Me included. I have my own tweets syndicated out so the same content appears on multiple sites. It's not a very effective way of doing it.
Has social media finally hit saturation point? I think the strategy has got to move away from 'be everywhere' and towards 'do a subset but do them very well'. For us, blogging and twitter have given the best yields. It's not a short term win - the time it takes does not result in an equal gain in sales, at least not straight away. Books sales often snowball. It takes sales to get sales, and with that comes a natural flow.
Social media doesn't have much effect. Some authors are prolific tweeters but only get a few dozen downloads. Some tweet not at all. The worst way is to automatically tweet the same thing over and over. Believe me, your followers will see it, but they won't often buy.
How many social media sites can one person really maintain? Does social media detract from writing for you? I'd like to propose an experiment. Stop all social media except for one channel (.e.g just twitter), and see if your sales drop. If it doesn't affect sales in a week, you've probably proved that social media isn't effective for you. If you're feeling really brave, see if no social media has any effect. I think you might be surprised.
Half an hour a day blogging/ tweeting etc is 14 hours a month. At a thousand words an hour, you've lost 168,000 words of writing time in a year. That's 2 novels a year you haven't published because of social media. Imagine how many more sales you'd have with the extra titles. Every bit of virtual shelf space helps, and a regular release schedule can bolster your income far more than telling everyone what you had for breakfast.