Check the comments too:

http://www.geekologie.com/2009/12/italy_google_street_view_wtf_i.php#comment

And the link to Google Maps:

http://maps.google.com/maps?source=embed&layer=c&cbll=42.36396,13.368008&cbp=13,320.72,,0,-29.96&ie=UTF8&panoid=K0Hv_pLb98MJa2Cd_QcH2w&ll=42.363907,13.367907&spn=0,359.997589&z=19

OMG! :o

It's a twig from a pine tree.

It appears it is on the lens:

http://maps.google.com/maps?source=embed&layer=c&cbll=42.364482,13.366814&cbp=13,259.02,,0,-24.58&ie=UTF8&panoid=kTpI1__Z3n4n9h0p6l56ng&ll=42.364422,13.36699&spn=0,359.995872&z=19

(link from Geekologie)