I am going to say no but there are lots of caveats haha!
In general, I don't think there is an issue with "too big". However, it depends upon the situation and context. Its perfectly OK to have a large diamond - but you have to be aware of the situation in which you are wearing it, and what you are wearing it with.
The rich and famous at their events wear priceless jewels a la Lady Gaga at the Golden Globes and she (and the diamond) looked absolutely spectacular. The necklace suited her outfit as well as the context in terms of the occasion. The event was a super fancy ball/event in which case the priceless diamond was hardly alone in that room with the other guests. Dressing up for that kind of occasion is very much expected.
As an example, and we change the context of Lady Gaga wearing that diamond to say the poorest areas of the world, in front of people suffering greatly, then I would say its not appropriate and is definitely tacky. The diamond itself has not changed, merely the situation surrounding the diamond. Wearing this in front of (as example only) people in the slums of Bangladesh, it would appear grotesque and almost unsightly to have the juxtaposition of extreme wealth with extreme poverty. (Not that lady gaga would do such a thing, im only using it to explain my pov, I think she looked amazing and gorgeous plus is so very talented, the same could be said for Kim Kardashian or any other famous person who have large expensive jewels).
I have a cocktail ring I bought at auction which is a 1.7ct centre stone and is the largest bling I own. Its definitely larger than my engagement ring. I only wear it to black tie events because I find I cant wear it day to day as its not appropriate.
Just my humble opinion. Thanks for the open honest discussion