Multiple wildcard dns entries

Are there any problems with having multiple wildcard dns entries for a domain?

Eg:

CNAME  *.a.example.com  1.1.1.1
CNAME  *.b.example.com  2.2.2.2
CNAME  *.example.com    3.3.3.3

I have this set up currently with DNSimple and it all seems to work ok, I'm just wondering if there are any potential issues.

With wildcard cname or a record, people can reach your site using

Any_Combination_Of_Inappropriate_Or_Embarrassing_Word.yourdomain.com

If some page in the wild link to your site with the above, when they indexed by search engine, your site may be associate with search item/terms/words you don't want. And you really have no control.

The above is the main reason I stay away from wildcard dns record.