Portfolio Diversity : invest $4000 into one account or $1000 into 4 accounts?
You spread money/investment across different accounts for different reasons: All this is in addition to diversification reasons. Investing all your money into one stock, bond, Mutual fund, ETF is risky if that one segment of the economy/market suffers.  There is a drawback to diversification of accounts. Some have minimum amounts and fee structures. In the original question you asked about 1,000 per account. That may mean that some accounts may be closed to you. In other cases they will charge a higher percentage for fees for small accounts. Those issues would disappear long before you hit the 1,000,000 per account you mentioned in your comment. One problem can occur with having too much diversification. Having dozens of funds could mean that the overlap between the funds might result in over investing in a segment because you didn't realize that one stock segment appeared in 1/3 of the funds.