Whatever you do, make sure it's secure. There are idiots who delight in defacing these things and most of them rely on technologies (PHP, SQL and CMS) which are easily hacked unless care is taken to secure them.
I would avoid using a public service, because they're usually set up for ease of access for newcomers and not for security, and I'd avoid using a pre-packaged piece of software for the same reason. Nor would I employ a developer I couldn't trust. Many of them will just grab one of the aforementioned off-the-shelf solutions and charge you a bomb for it.
That leaves you the unenviable task of building it yourself and securing it. I'd develop it in a virtual machine behind a firewall and only let it go live once it's fully working and toughened up.