Israel admits it spied on US — Taken from BBC news

I thought this is interesting because we always thought that Israel and US have open relations, apparanetly not for Israel.

This news and other bring me to the question who i still don’t have a satisfying answer for: Why the US is allied with Israel? what the US gain of the alliance? I see what Israel gains, but i don’t see what the US gains. The only half an answer I can think of, is because the Jewish lobbies in US spressuring it to stay an ally, otherwise i can’t see any good reason.
what is a lobby? Check this in wikiedia.org
http://en.wikipedia.org/wiki/Lobbying

Here is the BBC news:
[b]Israel admits it spied on US[/b]
Jonathan Pollard with Israeli communications minister Limor Livnat who visited him in prison
Israel has officially acknowledged for the first time that an American Jew, Jonathan Pollard, who was arrested in the United States 13 years ago, was one of its spies.

Pollard, a former intelligence analyst for the United States navy, is serving a life sentence in North Carolina for passing classified military documents to Israel.
*rest in the link below
http://news.bbc.co.uk/2/hi/americas/91260.stm