Hi Gus
On flowers, and backgrounds and angles and other stuff.
Personally I think all the rules are meant to be broken. One of the times I like to include the background is when it offers a good color contrast
Another time I like to include the background is when I want to give the impression of LOTS and LOTS of flowers.
Even if there is no distracting shapes/color in the background try to choose the angle that gives the most contrast. For instance a light colored flower against sunlit grass doesn't stand out as well as the same flower shown against a dark hedge or evergreen tree/shrub.
I don't mind OOF flowers in the background, sometimes they give actually help give context to the main subject. However I do prefer the background to be mostly smooth OOF more like your first sample.
Other things to consider.
Backlighting can work wonders, but you have to be careful of exposure, I almost always use spot metering and expose to (or at least towards) the highlights. This shot borders on over exposed, but I still like the play of light and shadow in it.
Don't be afraid to throw everything out the window and try something weird...it might just work out. This shot was taken from behind the flower. What you are looking at is the backside of the flower but I think it works.
One final comment. Flowers are a mixture of color, shape and texture. Sometimes a full profile shot is just ho hum while a direct face shot is Oh Wow! or vice versa. And sometimes a 3/4 view will be the best angle. I'd provide examples, but I think I'm coming close to hijacking this thread and that's not my intention. You can see lots and lots of flower shots at my smug mug site which unfortunately has been pretty neglected lately, check out both the "Flowers" category and the "Seasons" category if you want more examples.
http://saltwater.smugmug.com/
NaCl(hope this helps)H2O