There is a chance that spammers use your number to send you spam messages.
We all have this favorite expression when it comes to being stressed out, and I wouldn't bother naming all of them since it may also vary in different languages.
Wenn all das kein Problem für euch ist, spricht nichts dagegen, durch eine Online-Handynummer eure Privatsphäre zu schützen.
Other forms of verification can try to be a bit more secure by requiring you to enter more personal information like a name, address or zip code.
The available public numbers are for free usage and doesn't require you to pay any fees no matter how much sms you receive.
A temporary number will be a good replacement.