[wolfgang42]

Well, even if nobody else seeds you're still no worse off than you would be with just an HTTP server. At present the main incentive is generosity, which works pretty well for a lot of things; for example a lot of people started pinning the Turkish Wikipedia mirror when it was announced purely as a stand against censorship. In addition, you can also pay a pinning service. In the longer run the IPFS developers are also working on Filecoin, which is a cryptocurrency that adds a payments layer on top of IPFS so you can pay to have someone else serve your content.