I sit on both sides of the fence daily, using both FOSS and proprietary - and I wouldn't have it any other way. I use the environments and tools that my clients feel most comfortable with. If my clients want to hear about choice I tell them, if they don't - I won't. I am not an evangelist for either open or proprietary. Both have their strengths as they both have their weakenesses.
Karsten Gerloff, says, "Every time that state websites link to non-free applications and encourage visitors to use them, they needlessly encourage citizens to throw away their freedom". The problem I have with *some* FOSS advocates (not necessarily Karsten) is that, given the chance, they would love to remove my absolute freedom to choose by dictating that FOSS offerings should be the *only* option. To such FOSS bigots I say a big 'bollocks, just as I say 'bollocks' to proprietary bigots.
At the end of the day, if the uptake for certain FOSS offerings is somewhat low that would indicate 1 (or both) of 2 things; (1) The alternative is shite (and yes, there is some real open source shit out there, just as there is some awful proprietary shit), (2) That marketing is poor.
I agree however that government sites should offer alternatives. A fair place to start would be one FOSS offering for each proprietary offering. But let's not forget there are countless open souce applications out there that are poorly written and are not particularly security or performance conscious, just as there are proprietary.
Alternatives should be given, but only where such alternatives are truly fit for purpose and not just because they are FOSS.
Flame away ;o)