Many people wonder either how popular a name can be for it to be usable, or how unpopular a name can be to be usable. When does it become too popular, or too unusual? I know my preferences are different from the next person, perhaps even extremely different. I would choose a name that is not in the top 1000, and has not been in the top 1000 for the past decade, but is not a word, place, or thing, and is not made up. In other words, a legit name that the child will likely never see on someone else their age, but something easily understandable. Definitely not something like Expo, but maybe something like Verbena. But I've always been drawn to rare, historical, and mythological names, having a naturally rebellious and creative nature. Everyone else I know, even if they want their child's name to be unique, tends to go for names on the top 1000 list, with popularity being an afterthought.
So as general advice, here's what I suggest: don't choose an unusual name that is also akward, hurtful, or will give your child trouble. In other words, don't deviate from traditional spelling to the point where no one will ever spell it right (Anejelah instead of Angela), don't make up a name (Arjaiden), don't name them after an object (Video) or product (Nivea) or descriptive word (Shine). A name like Ursa is rare and will get weird looks at first, but your child will be able to confidently tell people about Ursa Minor and that it means "little bear." A name like Oreo, Swift, or Shimmer, will just get weird looks. Keep your options between rare legitimate names, and those that are not in the top 100 to 300. The reason I suggest it not be in the top 100 is because, for example, Leah currently ranks #24, there were 6474 baby girls born in 2010 named Leah, which means there were about 130 born with this name per state in just one year. This does not take into account all the previous years and fluctuations in popularity. So, better safe than sorry.
Everyone will be different. Maple is a good example. I'm sure last year everyone would have said "That's weird for a name," but this year it has gotten so popular that even a celebrity used it, but there are still those who refuse to accept it. So, some might consider Anielka crossing the line, but it is not offensive, akward, or too troublesome.