Lets go straight to the source aka Google. What does Google say about product titles and descriptions?
All your product submissions should follow three principles:
Be honest and factual.
Describe your message clearly and accurately.
Include relevant and complete information about your products with attributes.
In addition, make sure you:
Use standard spelling and grammar.
Avoid any repeated and unnecessary use of punctuation, capitalization or symbols. Don't use exclamation points in your product titles. The use of symbols, numbers, and letters should adhere to the true meaning of the symbol.
Avoid gimmicky repetition. You may not post excessive, repetitive, or irrelevant keywords such as APPLE IPOD I-POD I POD 80GB.
Avoid offensive or inappropriate language.
That seems pretty clear to me. I keep seeing people advising others that unnecessary symbols are okay as long as you leave a space. Not true! Notice what is says about repetitive keywords. But how many people have titles that are keyword stuffed.
Also tons of people that have "free shipping" in their title. Thats a Google no no. Heck Google does not even want shipping info in the description (which I am quilty of)
For the full article click here
I do think this is why a lot of people have their products disappear from Google shopping. If you continue to violate their policies they will ban you.