When I read about U.S. unions, it always reminds me of the German Zünfte from the medieval times : http://de.wikipedia.org/wiki/Zunft - Wikipedia translates this as "Guilds" : http://en.wikipedia.org/wiki/Guild

Wikipedia's description of Unions seems to say that U.S. Unions are different from German Gewerkschaften : The German Gewerkschaft is not mentioned in the English-language Wikipedia article on Unions.
U.S. Unions are, however, mentioned in the German-languge article on Gewerkschaften.

http://de.wikipedia.org/wiki/Gewerkschaft
http://en.wikipedia.org/wiki/Trade_union

Both cite massive losses of members during the last decades.

Edit SEIU seems to be quite … weird, I read now : http://en.wikipedia.org/wiki/Service…national_Union
This behaviour is alien to Germany. German Gewerkschaften are not like this, at least not that I know of.