I do not have the feeling. There aren't many postings and still every now and then some spammer appear and their posts are'nt deleted :(
They seem to me to get quite quickly deleted.
You realise you can report these posts - click 'Actions' and choose 'Report':
You can also report the spammer via their profile:
I often did (mainly posts with suspicious links), but many posts are still there after a week.
Hey Bastian, we do our best to catch and remove spam both automatically, and manually. You have the options that Andy mentions above to report spam, but you can also free to @mention me in any content that you think needs to be removed.