But, you can not honestly tell me that when someone bids from their broadband connection with only seconds remaining in the auction that they are doing so for any other reason but to make sure that no one can outbid them. ... (sorry for the run-on sentence!)

You need to have more confidence, dude! Other than misspelling ``cannot'' and the questionable grammatical structure of starting a sentence with a conjunction, both minor offences, IMHO, your sentence is perfectly grammatical, and not a run-on sentence at all. A run-on sentence is one that basically combines two or more separate sentences without a period, conjunction, or adequate punctuation, which yours is definitely not.

If only people would learn English (I don't have enough experience with bad grammar in other languages to speak authoritatively), they would be able to construct, and read, complex sentences without concern or confusion. Maybe if more schools taught Faulkner, complex sentence structure would be more common. It can be so boring to read the same ``Subject-Verb-Object'' sentences over and over. It's nice to see something else. So don't worry about making complex sentences. Just worry about your grammar.