I have always wanted to use Pipes, but unless I am misreading the Terms of Use (1.f.iv), it seems to suggest that you are not allowed to derive any income from any service that uses it.
YOU SHALL NOT:
Sell, lease, share, transfer, or sublicense Yahoo! Pipes or derive income from the use of Yahoo! Pipes in conjunction with Yahoo! APIs or other web services, whether for direct commercial or monetary gain or otherwise, without Yahoo!'s prior, express, written permission;
I'm perplexed as to why a company releases a brilliant product (I love graphical programming compared to coding) and then discourages people from using it for anything serious. No wonder they're in decline.