High Scalability Building bigger, faster, more reliable websites.

Hello, I am new to the back end side of things. Love this web site.
Read all comments about Amazon hosting, actually I really like Amazon S3 but concerned that it may not be sufficient for my computing needs. And E3 just not too sure.

What about hosting sites like host monster? Their prices seem amazing. Are they too good to be true? What are the cons and what are the things I should be considering? I am concerned about costs, but I want user experience to be world class.

I am creating a media sharing site.

Any help will be great.

Thanks

Fahad