Which main problems could arise from adding a number to a domain name?

Consider the domains star.com and star1.com.

What could be the problems with adding number as in the second example?

I can think about the following, I speak Hebrew and in Hebrew I could say:

star one dot com סטאר וואן דוט קום 

I could also say:

star ehad dot com סטאר אחד דוט קום 

(ehad in Hebrew means one).

Either of the Hebrew phrases might confuse a listener (vocally); the listener might not be sure if either "one" or "ehad" would mean an actual number 1.