I wrote a piece on the VaultPress blog recently about some basic security practices plugin developers should know and include in their own plugins.
This sums up my beliefs on being a plugin/theme developer:
Writing plugins for WordPress gives us so much freedom and flexibility on the platform and with this ability comes a responsibility to the community; a responsibility to develop secure plugins that the community can trust and use on their websites. And by doing so, we are making the web a better place.
Read the full article:
Five Ways to Secure Your WordPress Plugins