Are free BTC sites essentially useless?

[kaoD]

You can get a few microBTC out of free ad-supported sites but if I understand Bitcoin correctly that creates LOTS of inputs for my future transactions which will make it have fees of 500mBTC per kb, rendering the reaping essentially useless.

Am I missing something? Should I just stay away of these sites?

I know the profit is poor even if no transaction fees were involved but it seemed like a great way to make some of my friends "mine" some microBTC.

[Portnoy]

Many of the sites allow you to delay your payout until it builds up to an amount you
prefer to withdraw, which is in their best interest as well. 

I have never had any problem sending any of the BTC I have gotten.  Let it age, and
you can also add it as inputs to transactions involving larger amounts. 

And of course don't expect using these sites to be a way of getting rich.   
Its just a fun hobby for many... and:

What good is it if one only gets very very small amounts?
https://bitcointalk.org/index.php?topic=74046.msg1088930#msg1088930

[medicine]

I feel that these sites are useful because they give new adopters a chance to learn how to use the functions of their wallet (receiving coins, creating an address, understanding confirmations).  These sites help build interest in BTC everyday, when I first got my client I was using these sites everyday.

I don't like the gambling aspect of some of them, but that's just my personal opinion.

Peace