note1)You do this when the sentence is causal (1 part occurs and a result of the other part) Sometimes the infinitive can replace the gerund, for ex. : " I like to read" "I like reading", but not after the preposition "for" , when "for" means "because", only when "for" means "in order to/ for the purposes of" Look at this example: "This is a good place for eating." (Although I think some people would consider this a sub-standard way of saying it) "This is a good place to eat." Here "for" means "for the purpose of" "This is a good place for running/to run." "I have to send in this form - for completing/(in order) to complete - my Visa application." note 2) What the 2nd continuous verb is actually describing is the continuity of the verb in the 1st part of the sentence : It is his fame that you are remembering, it is your thankfulness that may continue throughout your life, it is the persistence of the memory. See in your first sentence you could say "He IS famous for speaking.." even if "he" is dead. When you say "was " you mean "still is". Whereas if you say "This was a good place for eating/running" clearly you mean it is not now. "I gave him money for buying food" is "for the purpose of" and using the past or present tense in the first part clearly shows whether the action is over or not. a: Why are you in prison? b: - I got into/I am in- trouble for breaking a window. "I remember when I got into trouble for breaking a window." I think it shows some subjunctive tendencies (remorse , regret, memory, emotion).

ooops , sorry , I meant ,"in your examples u'r talking about a cause not a purpose" ..... :D so you use" for" which means" because of" ( they express a cause ) , u can't use" to" coz it means " in order to" ( both of " to" and " in order to" express a purpose" )

in your examples u'r talking about a cause or a purpose , " for" has the same meaning as" because of" , if you try to form a question of each sentence , u say"what was he famous for ?" , or" he was famous because of what" , same goes for second and third sentence" what are you thanking me for ?" or " you're thanking me because of what ?" , but if u use " because of" the sentence will sound a little odd , so it's better to use" for" , to make it easy for ya , in french we say" il est connu POUR qlq chose " or " il est connu POUR avoir fait qlq chose", " le mot" pour" here has same fonction as" for" in english u can replace " to" by" in order to" when you talk about a purpose,like in michael's example --> " he gave me money IN ORDER TO" ..... and in your examples u can't say" he was famous IN ORDER TO speak first and think afterwards" ; " thank you IN ORDER TO be with us"

It's a good question for me too because I haven't seen or developed a comprehensive answer to this question. Sometimes you can have both, but like in your sentences, sometimes only one option is correct. It might help to formulate questions which the statements answer e.g. What was he famous for? What do you want to thank us for? (more information needed) Why did he give you money? (reason) He gave me money to buy some food What did he give you money for? He gave me money for buying some food. The second option is OK but, to me, doesn't sound as good as the first. I'd be interested to see other answers.

Thanks ! :-)