Why would scientists share data?

F1000Research is an open access journal for life scientists, with rapid publication, transparent peer review (post-publication) and full data deposition and sharing. Open Access Journal have been widely discussed. I have talked about it here. However, sharing data is barely discussed. This journal has recently shared their experience with data openness:
http://blog.f1000research.com/2013/03/14/data-why-openness-and-sharing-are-important/

They raised several important questions, such as verification of results/conclusions, attracting collaborators or establish that you were the first to obtain those data. Scientists have also been questioned about their views and reported in Data Sharing by Scientists: Practices and Perceptions.

As a researcher, I have sometimes data which I would like to share (patient data can't be shared of course...), but I am torn between "I can't write a paper about the data itself" and "If I share it without caution, someone will use my data and not even acknowledge me and it gave me so much work!".

Did you ever considered sharing your data?