I have a ton of plastic showing that I am a frequent flyer at Delta, El Al, Lufthansa, KLM, AA, and a few regional airlines. I also have membership at Hertz, Avis, Dollar and Budget as well as at about 15 hotel chains.

Before I fly, drive, or stay with any company I get their card. Why? Because it can't hurt. It may only get me free local calls at Hampton Inn or a newspaper somewhere else, but it may also let me into a better room which is reserved for members.

Having said that, I *NEVER* fly, drive, or take a hotel room based on my membership cards. I always go for the best price and tale whatever points they might give me. (This year it was enough for Gold Medallion at Delta, but I could have been Platinum if I had changed some El Al and Lufthansa flights to Skyteam members.)

Points/miles are simply not worth additional costs.

Assume, for example, that I take ten flights this year. Four are from Israel to the East Coast and 6 are from Israel to Western Europe. If I make them all on Delta/Skyteam, I will get about 75,000 miles.
Let's be generous and say 80,000 -- which earns me one free round trip from Tel Aviv to the US.

By seeking the lowest fares to the US, I can save about $300 per trip. To Europe, I will save about $200. Total savings: $2400.

With that $2400 I can get TWO round trips to the States. More than that, I don't have to book years in advance to assure that a free seat will be available and I can take my trips on any airline that I want.

Yes, join any and all clubs and yes, take the miles/points when they are offered -- just don't plan your trip in order to get them.