Without trawling through all the previous posts (somebody has already similar) but opening the scheme up to casual users IMO is only a good thing; Joe Bloggs is driving to work for several days in a row, stuck in jams etc with bikes going flying passed him; one morning he wakes up (a beautiful summers day) and decides on the spur of the moment to try out this cycling lark, likes it and becomes a regular cyclist. Encouraging modal shift isn't as simple as that but a registration scheme puts another barrier on it (ie its makes it harder for spur of the moment decisions).
A bit OT but on my youtube
links, yesterday was a link to the similar Melbourne Bike Scheme, the poster was suggesting its a failure because of restrictions it places on spur of the moment decisions (in Victoria's case their helmet laws).