Guppies Compatible W/Platy's?

[Gettin' Tanked]

I am currently stocking a 30 Gal. community aquarium and was considering putting a school of fancy guppies in with my zebra's and platy's. However, I recently read on a website that guppies and platy's are not compatible tankmates but it offered no explanation as to why. Can anyone shed some light on this for me?

Thanks!

[PumaWard]

They may interbreed, which would produce undesirable offspring would should never go into circulation.

I wouldn't add the guppies, more so though, because of the danios. I haven't had good experience with it (the danios harassed the guppies).